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Kinases catalyze the transfer of a phosphate group from adenosine triphosphate (ATP) to give adenosine diphosphate (ADP) and a ______.
phosphorylated product
Hydrolases catalyze a hydrolysis reaction in which the addition of a water molecule to a bond causes the bond to ______.
break
Prosthetic groups are tightly incorporated into protein structure by covalent or noncovalent ______.
forces
The suffix -ase identifies a substance as an ______.
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Examples of prosthetic groups include derivatives of B vitamins such as pyridoxal phosphate, flavin mononucleotide (FMN), and ______.
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Lyases catalyze the addition of a group to a double bond or the removal of a group to form a double bond in a manner that does not involve ______.
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Carbohydrases effect the breaking of glycosidic bonds in oligo- and ______.
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Thiamin (B-1) is also associated with a coenzyme known as ______.
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Chirality is inherent in an enzyme active site because amino acids are ______ compounds.
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An L-amino acid oxidase will catalyze the oxidation of the L-form of an amino acid but not the ______ form.
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The degree of enzyme specificity is determined by the ______ site.
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Enzyme activity is a measure of the rate which an enzyme converts substrate to ______ in a biochemical reaction.
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Absolute specificity refers to an enzyme that will catalyze only ______ reaction.
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Catalase is an enzyme with absolute specificity; it catalyzes the conversion of hydrogen peroxide (H2O2) to ______ and H2O.
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When the temperature increases beyond a certain point, the increased energy begins to cause disruptions in the ______ structure of the enzyme.
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Denaturation occurs when the tertiary structure at the active site is ______.
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An enzyme is produced from an apoenzyme and a ______.
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Most enzymes are composed of ______ proteins.
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Enzymes cause cellular reactions to occur millions of times faster than corresponding ______ reactions.
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Cofactors for enzymatic reactions may include vitamins and ______.
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The inactive form of the apoenzyme is known as a ______.
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A simple enzyme is composed only of ______.
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Cofactors can provide additional chemically reactive ______ groups.
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Common cofactors include ______ ions like Zn and Mg.
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Enzyme activity is dramatically affected by changes in ______.
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The protein part of a conjugated enzyme is referred to as an ______.
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The products must leave the site before the ______ can be repeated.
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Turnover Number is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of ______, pH, and saturation.
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If the amount of substrate present is kept constant and the enzyme concentration is increased, the ______ rate increases.
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A noncompetitive inhibitor binds to a site on an enzyme other than the ______ site.
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An irreversible inhibitor inactivates enzymes by forming a strong ______ bond to an amino acid sidechain group at the enzyme’s active site.
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A competitive inhibitor sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s ______ site.
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Enzyme inhibitors slow or stop the normal ______ function of an enzyme by binding to it.
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Increasing enzyme concentration will ______ the rate of reaction.
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Vitamin B12 is also known as ______.
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Water-soluble vitamins circulate in the ______-filled parts of the body.
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Fat-soluble vitamins tend to remain in ______-storage sites.
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Excess vitamin B12 is removed from the body by the ______.
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Vitamin B6 is also referred to as ______.
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Vitamin B1 is commonly known as ______.
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Folate is also known as ______ acid.
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Coenzyme A (CoA) is associated with ______ acid.
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Vitamin B12 transfers ______ groups and hydrogen atoms.
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Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
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An oxidase enzyme catalyzes an ______ reaction.
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A hydrolase enzyme catalyzes a ______ reaction.
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Oxidoreductase is an enzyme that catalyzes an ______ reduction reaction.
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Transferase enzymes are involved in the transfer of a ______ group.
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A transaminase catalyzes the transfer of an ______ group.
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Coenzyme A (CoA) is associated with ______ acid.
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Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
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Enzymes that catalyze the addition of a group to a double bond are classified as ______.
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Each substrate must occupy an enzyme active site for a finite amount of time, and the products must leave the site before the cycle can be __________.
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Turnover Number is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of temperature, pH, and __________.
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If the amount of substrate present is kept constant and the enzyme concentration is increased, the reaction rate __________.
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A noncompetitive inhibitor is a molecule that decreases enzyme activity by binding to a site on an enzyme other than the __________ site.
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An irreversible inhibitor inactivates enzymes by forming a strong __________ bond to an amino acid sidechain group at the enzyme’s active site.
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A competitive inhibitor sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s __________ site.
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Enzyme inhibitors slow or stop the normal catalytic __________ of an enzyme by binding to it.
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Increasing enzyme concentration will __________ the rate of reaction.
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Statins are known as HMG Coenzyme A reductase inhibitors which lower serum ______ concentration.
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Emtricitabine and Tenofovir Disoproxil Fumarate are inhibitors of viral reverse ______.
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Angiotensin Converting Enzyme (ACE) inhibitors interfere with the body’s ______ System.
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Lactam antibiotics, such as Penicillin, inhibit ______ synthesis by targeting bacterial enzymes.
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Sulfa drugs mimic ______, which is vital for folic acid synthesis in bacteria.
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Lactate Dehydrogenase (LDH) is an enzyme associated with possible tissue damage, particularly in cases of heart and ______ disease.
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Water-soluble vitamins, including Vitamin C and B6, circulate in ______-filled parts of the body.
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Excess vitamin B12 is removed from the body via the ______.
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An enzyme that catalyzes the isomerization of a substrate is called an ______.
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The enzyme that catalyzes the bonding of two molecules with the participation of ATP is known as a ______.
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Oxidoreductase enzymes are involved in ______ reactions.
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Chymotrypsin is an example of a type of enzyme known as a ______.
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The part of the enzyme's structure that is involved in catalysis is called the ______ site.
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The process by which an enzyme's activity is reduced or stopped is referred to as ______.
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The term for enzymes that only catalyze a single reaction is called ______ specificity.
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Vitamins may act as ______ for enzymatic reactions, helping to facilitate various biochemical processes.
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Vitamin B12 is also known as ______.
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Water-soluble vitamins circulate in the ______-filled parts of the body.
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Fat-soluble vitamins tend to remain in ______-storage sites.
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Excess vitamin B12 is removed from the body by the ______.
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Coenzyme A (CoA) is associated with ______ acid.
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Folate is also known as ______ acid.
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Vitamin B6 is also referred to as ______.
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Vitamin B1 is commonly known as ______.
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Vitamin B12 transfers ______ groups and hydrogen atoms.
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Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
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Study Notes
Enzymes
- Enzymes are biological catalysts, primarily proteins that accelerate biochemical reactions.
- Majority of enzymes are globular proteins, capable of undergoing denaturation.
- Enzymes accelerate cellular reactions, achieving rates millions of times faster than their uncatalyzed counterparts.
- Enzyme activity is significantly influenced by factors like temperature, pH fluctuations, and denaturants.
- Enzymes are classified structurally into two primary categories:
- Simple Enzymes: Comprised solely of protein (amino acid chains).
-
Conjugated Enzymes: Contain a nonprotein component in addition to protein.
- Apoenzyme: The protein portion of a conjugated enzyme. Its inactive form is known as Proenzyme/Zymogen.
- Cofactor: The nonprotein component of a conjugated enzyme, sometimes referred to as coenzymes. They provide additional chemically reactive functional groups.
Enzyme Cofactors
- Cofactors are molecules that assist enzymes in their catalytic activity.
- Common cofactors include vitamins and metal ions.
- Metal ion activators are inorganic and bind through coordinate covalent bonds. Examples include Zn, Mg, Mn, Fe, Cu, K, and Na.
- Holoenzyme: The active form of a conjugated enzyme, formed by the combination of an apoenzyme and a cofactor.
Enzyme Structure
- The structure of an enzyme's active site dictates its specificity.
- Enzyme specificity refers to the degree to which an enzyme's activity is restricted to a certain substrate, group of substrates, bond type, or reaction type.
- Absolute Specificity: The enzyme catalyzes only one reaction with a single substrate. This is highly restrictive and uncommon. Catalase is an example, converting hydrogen peroxide to O2 and H2O.
Enzyme Nomenclature
- The suffix '-ase' identifies a substance as an enzyme. Examples include urease, sucrase, and lipase.
- The type of reaction catalyzed by an enzyme is often indicated using a prefix.
- Chirality is inherent in an enzyme's active site due to the chiral nature of amino acids. For instance, an L-amino acid oxidase will catalyze L-amino acid oxidation, but not its D-isomer.
Factors Affecting Enzyme Activity
- Enzyme Activity: Reflects the rate at which an enzyme transforms substrate into products in a biochemical reaction.
- Four key factors affecting enzyme activity:
- Temperature: Enzyme activity increases with temperature until an optimal point is reached. Further increases lead to denaturation and reduced activity.
- pH: Enzymes have optimal pH ranges, deviating from which alters structure and reduces activity.
- Substrate Concentration: Increased substrate concentration results in increased reaction rate until saturation is reached (all active sites are occupied).
- Enzyme Concentration: Increasing enzyme concentration at constant substrate levels increases reaction rate as more substrate molecules can be accommodated.
Enzyme Inhibition
- Enzyme Inhibitor: A molecule that reduces or halts an enzyme’s normal catalytic function by binding to it.
- Types of Inhibitors:
- Competitive Inhibitor: Resembles the substrate in shape and charge, competing for the enzyme's active site.
- Noncompetitive Inhibitor: Binds to a site on the enzyme other than the active site, decreasing enzyme activity.
- Irreversible Inhibitor: Inactivates enzymes by forming a strong covalent bond with an amino acid sidechain group at the active site.
Enzymes in Clinical Use
- Certain enzymes are targets for drug actions.
- Turnover Number: The number of substrate molecules transformed per minute by a single enzyme molecule under optimal conditions.
Vitamin B
- The B Vitamins are structurally diverse and are major components of coenzymes.
- Preferred and alternative names for B vitamins:
- Thiamin - Vitamin B1
- Riboflavin - Vitamin B2
- Niacin - Nicotinic acid, Nicotinamide, Vitamin B3
- Vitamin B6 – Pyridoxine, Pyridoxal, Pyridoxamine
- Folate – folic acid
- Vitamin B12 – cobalmin
- Pantothenic acid – Vitamin B5
- Biotin – Vitamin B7
B Vitamins and Coenzymes
- Thiamin (B1): Thiamin pyrophosphate (TPP) – Transfers aldehydes
- Riboflavin (B2): Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) – Transfers hydrogen atoms
- Niacin (B3): Nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) – Transfers hydrogen atoms
- Pantothenic acid (B5): Coenzyme A (CoA) – Transfers acyl groups
- Vitamin B6: Pyridoxal-5-phosphate (PLP), pyridoxine-5’-phophate (PNP), pyridoxamine-5’-phosphate (PMP) – Transfers amino groups
- Biotin (B7): Biotin – Transfers carbon dioxide (Carboxyl group)
- Folate: Tetrahydrofolate (THF) – Transfers one-carbon groups other than CO2
- Vitamin B12: Methylcobalamin – Transfers methyl groups and hydrogen atoms
Vitamin A
- Four Major Functions:
- Vision: Key component of rhodopsin, a light-sensitive pigment in the retina.
- Growth and Development: Essential for normal growth and development, particularly of epithelial tissues.
- Immune Function: Supports immune system function by maintaining healthy epithelial barriers.
- Reproduction: Plays a role in male reproductive health, including sperm production.
Vitamin E
- Four Major Functions:
- Antioxidant: Protects cell membranes from oxidative damage.
- Immune Function: Supports immune system health.
- Blood Clotting: May influence blood clotting.
- Nerve Function: May be involved in nerve function.
Water-Soluble vs. Fat-Soluble Vitamins
| Category | Characteristics | Examples |
|---|---|---|
| Water-Soluble: | - Directly absorbed into the bloodstream. - Travel without carriers. - Circulate in the body's water-filled spaces. - Stored in the body but not for prolonged periods. - Excreted in urine. - Less likely to reach toxic levels. - Required in frequent doses. - Often function as coenzymes. | B Vitamins, Vitamin C |
| Fat-Soluble: | - Enter the lymph first. - Many need protein carriers. - Found in cells associated with fat. - Stored in fat storage sites. - Can reach toxic levels with excessive intake. - Needed in periodic doses. - Do not function as coenzymes. | Vitamins A, D, E, K |
Enzymes Overview
- An enzyme is a protein that catalyzes a specific chemical reaction in the body.
- Enzymes have an active site that binds to the substrate, the molecule on which the enzyme acts.
- The suffix "-in" is often used in enzyme names, such as trypsin, chymotrypsin, and pepsin.
- Six main classes of enzymes:
- Oxidoreductase: Catalyzes an oxidation-reduction reaction.
- Transferase: Transfers a functional group from one molecule to another.
- Hydrolase: Catalyzes hydrolysis reactions.
- Lyase: Adds or removes groups to/from double bonds.
- Isomerase: Rearranges atoms within a molecule.
- Ligase: Joins two molecules together.
Models of Enzyme Action
- Lock-and-key model: the active site of an enzyme is a perfect fit for the substrate.
- Induced fit model: The active site of an enzyme changes shape to fit the substrate.
Enzyme Concentration
- As enzyme concentration increases, the reaction rate increases, as more substrate molecules can be accommodated.
Enzyme Inhibition
- Enzyme inhibitors: molecules that slow or stop enzyme activity by binding to the enzyme.
- Competitive inhibitors: Molecules that bind to the active site, competing with the substrate.
- Noncompetitive inhibitors: Molecules that bind to a site on the enzyme other than the active site.
- Irreversible inhibitors: Molecules that inactivate enzymes by forming a strong covalent bond with the active site.
Enzymes in Clinical Use
- Statins: Inhibit HMG CoA reductase to lower serum lipid concentration.
- Emtricitabine and Tenofovir Disoproxil Fumarate: Inhibit viral reverse transcriptase to block HIV replication.
- ACE inhibitors: Inhibit the conversion of angiotensin I to angiotensin II, lowering blood pressure.
- Lactam antibiotics: Inhibit alanyl alanine carboxypeptidase transpeptidase, blocking cell wall synthesis in bacteria.
- Sulfa drugs: Mimic PABA, hindering bacterial growth by interfering with folic acid synthesis.
Selected Blood Enzyme Assays
- Lactate Dehydrogenase (LDH), Creatinine Phosphokinase (CPK), Aspartate Transaminase (AST), Alanine Transaminase (ALT), Gamma-glutamyl Transpeptidase (GGTP), and Alkaline Phosphatase (ALP) are enzymes used in diagnostic medicine to assess tissue damage and disease.
Vitamins
- Vitamins are organic compounds essential for human health obtained from dietary sources.
- Water-soluble vitamins are absorbed directly into the bloodstream and excreted in urine.
- Fat-soluble vitamins are absorbed into the lymph system and stored in fat-storage sites.
Vitamin B
- A group of structurally diverse vitamins that are essential for the functioning of coenzymes.
Vitamin A
- Essential for vision, growth, and immune system function.
- Forms retinol, retinal, and retinoic acid.
Vitamin E
- An antioxidant that protects cell membranes from damage.
- Also known as tocopherol.
Vitamin D
- Essential for calcium absorption and bone health.
Vitamin K
- Essential for blood clotting.
Co-enzymes
- Coenzymes are non-protein organic molecules that assist enzymes in catalyzing reactions.
- Many B vitamins are components of coenzymes.
- Coenzymes do not undergo permanent chemical change
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Test your knowledge on enzymes and their cofactors with this quiz. Explore key concepts like enzyme classification, structures, and the factors influencing enzyme activity. Perfect for biology students looking to deepen their understanding of biochemical reactions.
