Enzymes Introduction Notes PDF

# ENZYMOLOGY ## 27/01/2025 ## ENZYMES - hastens chemical reactions in organic matter - catalyzes single or limited number of chemical reactions - large molecules confined in cells - increase membrane permeability allows them to enter the blood - measured in terms of their activity and not of thei...

# ENZYMOLOGY ## 27/01/2025 ## ENZYMES - hastens chemical reactions in organic matter - catalyzes single or limited number of chemical reactions - large molecules confined in cells - increase membrane permeability allows them to enter the blood - measured in terms of their activity and not of their absolute values - appear in serum after cellular injury, degradation of cells or from storage areas - used clinically as evidence of organ damage pero di pangdiagnose - specific for substrate that it converts to a defined product ## ENZYMES Each enzyme contains: 1. **Active site** - water free cavity where the substrate interacts 2. **Allosteric site** - cavity other than the active site - bind regulator molecules ## ES COMPLEX - physical binding of a substrate to the active site of an enzyme ## FACTORS ### A. **ENZYME CONCENTRATION** - the higher enzyme concentration, the faster is the reaction ### B. **SUBSTRATE CONCENTRATION** - with the amount of enzyme exceeding the amount of substrate, the reaction rate steadily increases as more substrate is added - **saturation kinetics:** when the substrate concentration reaches its maximal value, higher concentration substrate no longer result in increase rate of reaction ### C. **COFACTORS** 1. **Coenzymes** - helps substrate to fit on second substrates (organic compound) - ↑ coenzyme = ↑ velocity of reaction - essential for absolute enzymatic activity - ex. NAD and NADP 2. **Activators** - inorganic ions - alters spatial configuration of enzyme for proper binding - ex. calcium, zinc, chloride, magnesium, potassium 3. **Metalloenzymes** - inorganic ions attached to a molecule - ex. catalase and cytochrome oxidase ### D. **INHIBITORS** 1. **Competitive Inhibitor** - binds to active site of enzyme - substrate and inhibitor compete for same site of enzyme - substrate > inhibitor = reversible reaction - inhibitor excess substrate has the ability to alter Km 2. **Non competitive Inhibitor** - does not compete with substrate (allosteric site) - irreversible inhibition - enzyme + inhibitor = no reaction 3. **Uncompetitive Inhibitor** - inhibitor binds to ES complex - ↑substrate = ↑ ES = ↑ inhibition ### E. **ISOENZYMES** - same catalytic reaction but slightly different molecular structure - varies from amino acid sequence - ↑ enzyme activity + isoenzyme ### F. **TEMPERATURE** - ↑temp = ↑activity of chem reactions - active: 25°C, 30°C, 37°C (optimum) - denatured: 40°C to 50°C - inactivated: 60°C to 65°C - ↑ temperature = movement of molecules = ↑ reaction - **temperature coefficient (Q10):** ↑ 10°C = two fold in enzyme activity ### G. **HYDROGEN ION CONCENTRATION or pH** - physiologic reactions: pH 7 to 8 - extreme level pH: - denature enzyme - influence ionic state - structural change - change in charge of amino acid residue in the active site ### H. **STORAGE** - low temperature (refrigeration/freezing): reversibly inactive - repeated freezing and thawing: denature proteins - -20°C: preservation for long period - 2°C to 8°C: ideal storage for substrate and coenzyme - RT: ideal storage for LD (LD4 and LD5) ### I. **HEMOLYSIS** ↑ enzyme concentration kaçi pumutok ang rbo ### J. **LACTESCENCE or MILKY SPECIMEN** enzyme concentration ## 2. ENZYME NOMENCLATURE ### ENZYME NOMENCLATURE - standardized by Enzyme Commission (EC) in 1961 and revised in 1972 and 1978 - classified according to: - biochemical function - substrate catalyzed - class of reaction catalyzed - individual identification numbers | ENZYME | ABBREVIATION | IDENTIFICATION NUMBER | | :--- | :---: | :---: | | Acid phosphatase | ACP | 3.1.3.2 | | Aldolase | ALD | 4.1.2.13 | | Alkaline phosphatase | ALP | 3.1.3.1 | | Amylase | AMS | 3.2.1.1 | | Alanine aminotransferase | ALT | 2.6.1.2 | | Aspartate aminotransferase | AST | 2.6.1.1 | | Aldolase | ALD | 4.1.2.13 | | Angiotensin converting enzyme | ACE | 3.4.15.1 | | Creatine kinase | CK | 2.7.3.2 | ## 3. ENZYME CLASSIFICATION ### ENZYME CLASSIFICATION | CLASS | FUNCTION | EXAMPLE/S | | :--- | :--- | :---: | | 1. Oxidoreductases | catalyze the removal or addition of electrons (redox) | Cytochrome oxidase (CO), Lactate dehydrogenase (LD), Malate dehydrogenase (MDH), Isocitrate dehydrogenase (ICD), Glucose-6-phosphate dehydrogenase (G-6-PD) | | 2. Transferases | catalyze the transfer of a chemical group other than hydrogen from one substrate to another | Creatine kinase (CK), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), (OCT) | | 3. Hydrolases | catalyze hydrolysis or splitting of a bond by the addition of water | Esterase: Acid phosphatase (ACP), Alkaline phosphatase (ALP), (CHS), Lipase (LPS) | | 4. Lyases (lyse) | catalyze removal of groups from substrates without hydrolysis | Glutamate decarboxylase (), Pyruvate decarboxylase (), Tryptophan decarboxylase (), Aldolase (ALD) | | 5. Isomerases | catalyze the intramolecular arrangement of the substrate compound | Glucose phosphate isomerase (), Ribose phosphate isomerase () | | 6. Ligase |catalyze the joining of two substrate molecules coupled with breaking of pyrophosphate bond in ATP or similar compound | Synthase | ## 4. ENZYME THEORY - **LOCK AND KEY THEORY** - The shape of the key (substrate) must fit into the lock (enzyme). - **INDUCED FIT THEORY** - The substrate binding to the active site of the enzyme. ## 5. ENZYME KINETICS ## 6. ENZYME REACTIONS ### ENZYME REACTIONS - **ENZYME KINETICS** - ↑ free energy or kinetic energy on substrate + ↑ free energy or kinetic energy an product = ↑ chemical reaction - **ENZYME SPECIFICITY** - **Absolute specificity:** combines with only one substrate and catalyzes only one reaction - **Group specificity:** combines with all the substrates in a chemical group - **Bond specificity:** reacting with specific chemical bonds - **ENZYME REACTION** - **Zero order reaction:** depends on enzyme concentration - **First order reaction:** directly proportional to substrate concentration - **GENERAL METHODS** - **Fixed time:** reactants combined → reaction on designated time → reaction stopped measurement - **Continuous monitoring/ Kinetic assay:** multiple measurements, more preferred aver fixed time - **ENZYME REACTION** - **UNITS FOR ENZYMATIC ACTIVITY** - **International unit (IU or U):** 1 micromole of substrate/minute - **Katal unit (KU):** 1 mole of substrate/second - **REMEMBER** - Enzymes are quantified based on their activity rather than absolute values - change in substrate concentration - change in product concentration - change in coenzyme concentration - Units used to report enzyme levels are activity units - Definition for activity unit must consider change in pH, temperature, substrate, etc. - **ENZYME REACTION** - **CAUSES OF ELEVATED PLASMA ENZYME LEVELS** - Impaired removal of enzyme from plasma - Increase permeability of cell membrane - Increase in the number of cells or the production of cells - Increase in the normal cell turnover - Decrease clearance of enzymes from the circulation - Tissue necrosis and degeneration ## THANKS! - Don't forget you're human. It's okay to have a meltdown. - Just don't unpack and live there. Cry it out. - Then refocus on where you're headed.