Protein PDF

# Protein ## N.ppt - Introduction - Amino Acids (AAs) - Metabolism of Proteins - Non protein nitrogen and urea feeding to ruminant animals - Protein Anomaleis - Protein Evaluation ## Introduction: - Proteins take its name form the Greek word proteios, which mean first or primary in importance. - Pr...

# Protein ## N.ppt - Introduction - Amino Acids (AAs) - Metabolism of Proteins - Non protein nitrogen and urea feeding to ruminant animals - Protein Anomaleis - Protein Evaluation ## Introduction: - Proteins take its name form the Greek word proteios, which mean first or primary in importance. - Protein is a complex organic compound composed of carbon (51-55%), Hydrogen (6.5-7.3%), oxygen (21-23.5%), nitrogen (15.5-18%), sulfur (0.5-2%), phosphorous (0.05%). ## Classification of protein: The most widely used classification divides proteins into 3 main groups, which are: 1. Simple (fibrous or globular). 2. Conjugated. 3. Derived. Each of these groups then subdivided into a number of classes. ### 1. Simple proteins: These proteins yield only on hydrolysis amino acids or their derivatives. It could be classified into: #### A. Fibrous proteins: It is insoluble animal protein, composed of extended or coiled peptide chains that are highly resistant to digestion by proteolytic enzymes. It includes: 1. **Collagen:** This is the major protein of connective tissue in bone cartilage and tendons, it forms about 50% of the animal tissues protein. It is high in glycogen, proline, hydroxy proline and hydroxy lysine. It forms easily digestible, soluble gelatins by boiling in water or in dilute acids and alkalis. 2. **Elastin:** This is a protein of elastic tissues such as arteries, ligaments, and tendons. Elastin is easily digested by proteolytic digestive enzymes pepsin and trypsin but does not form gelatin in boiling water. It is formed from desmomine, which is derivative of lysine. 3. **Keratin:** This is a protein of feather, wool, hooves, beaks, nails and all the integumes (protective proteins). Keratin is very indigestible. It has coiled peptide chains of amino acids. Keratin contains about 15% cystine. 4. **Myosin:** Protein in contractile muscle. 5. **Fibrin:** The protein of the blood clot, formed from a more soluble form, fibrinogen, when clotting must occur. #### B. Globular Protein: They include enzymes and hormonal proteins. They are soluble in water and coagulable by heat. It includes: 1. **Albumins:** It occurs in eggs, milk, and blood. Also it is found in legumelin of peas and leucosin of wheat. Although albumins classed as simple proteins, egg albumin and serum albumin do not consists solely of amino acid but also contain carbohydrate. ### II. Conjugated proteins: These are simple protein combined with some non-protein substance (called a prosthetic group). It includes: 1. **Nucleoproteins:** It combined with nucleic acids as the prosthetic group. These are the proteins of the cell nucleus and of chromatin. It is found in germs of seeds, glandular tissue and sperms. 2. **Glycoproteins:** Not high in carbohydrates, but generally contain about 4% firmly bound hexosamine. It is found in serum albumin and globulin, egg albumin, gamma globulin. 3. **Mucoproteins:** It combined with mucopolysacharides such as hyaluronic acid. They are high in N-acetyl-hexose amine such as glucosamine and galactosamine. They are found in tendo-mucoid, chondro-mucoid of connective tissues in tendons, bones and cartilage. Also in animal mucins, ovomucoids. 4. **Lipoproteins:** A large biologically important class of water-soluble proteins conjugated with lipids such as lecithins, cephalins, cholesterol, and fatty acids. They are included in thromboplastin and rhodopsin, lipoprotein plasma, milk, egg yolk, cell membranes, and cell nuclei as well as chlorplasts of plants. 5. **Chromoprotein:** It conjugated with some pigments. It includes hemoproteins like hemoglobin, cytochrome and flavoproteins. Rhodopsin which is a lipoprotein, is also a chromoprotein, black wool and hair contain chromoproteins. 6. **Phosphoproteins:** It conjugated with phosphoric acid. They are linked to the phosphoric acid as an ester through the hydroxyl group of serine. It is found in casein of milk and vitellin of egg yolk. 7. **Metalloproteins:** Proteins conjugated with metals such as Fe, Co, Cu, Mn and Zn. Many enzymes as carbonic anhydrase are metalloprotines. So are ferritin, hemocyanin, hemoproteins and metal flavoproteins. ### III. Derived proteins: The definition of this group is that proteins produced from the degradation of naturally occurring proteins by the action of heat, enzymes or chemical agents like peptone and peptides with no hydrolytic cleavage. ## Functions of protein: Proteins play vital roles in every living cell. Some functions as enzymes, others as hormones, combined with other substances, are structural components of cell protopism and of membranes. - Proteins are involved in oxygen and other nutrients transport (blood Hb), muscle contraction (myosine), acid-base balance, osmotic pressure regulation, immunity (Ab) Bblood clotting, and heredity functions genes). - Proteins are major component of blood, muscles, and connective tissues in animals. Excess protein break down and liberate energy. One gram of protein liberates about 4.3 K calories. - Protein is important in formation of melanin (pigments of skin and hair), rhodopsin in eye, bile acids (taurocholic and glycoholic acids from the amino acids tyrosine and glycine, respectively). - Also milk protein and antibodies in colostrum (Immunoglobuline) of lactating animals. ## Chemical structure: The basal unite of protein structure is the amino acid, so any study of protein deals primarily with amino acids. Protein can be hydrolyzed, by boiling in alkali (2 N Na OH) for several hours or by refluxing with 6 N HCI for 20-40 hours, to its constituents of amino acid. The general formula for the naturally occurring amino acid could be shown as follow: $NH_2$ R-CH-COOH ## Amino acids classification: ### A. They are classified chemically into: 1. **Aliphatic:** which is subdivided to: - a- Mono amino, mono carboxylic (neutral): which include the amino acids glycine, alanine, valine, leucine, isoleucine and theronine. - b- Mono amino dicarboxylic (acidic): which include the amino acids aspartic acid and glutamic acid. - c- Di amino-monocarboxylic (basic) and this group include amino acid lysine, Hydroxylysine and arginine. - D-Sulfur-containing group which include sulfur in their AAs composition as methionine and cysteine. 2. **Aromatic amino acids:** This group contains the AAs phenylalanine and tyrosine. 3. **Heterocyclic:** As proline, hydroxyproline, tryptophan and histidine ### B- Glucogeniec and Ketogenic Classification of Amino Acids: Amino acids are also classisied according to their catabolic fates into: 1. Glucogenic. 2. Keto-geinc. 3. Glucogeinc and/or ketogeinc | Amino acid | MWz | Nature | Subclass | General class | |-----------------------|-----|--------|----------------------------------------------|----------------| | Arginine | 174 | G | Aliphatic straight chain | Basic | | Histidine | 154 | G | Branched chain | | | Lysine | 146 | GK | Hydroxylated | | | Aspartic acid | 133 | G | | Acidic | | Glutamic acid | 147 | G | | | | Alanine | 89 | G | | Neutral | | Glycine | 75 | G | | | | Isoleucine | 131 | G | | | | Leucine | 131 | K | | | | Serene | 105 | G | | | | Threonine | 119 | G | | | | Cystine | 240 | GR | Sulfur-containing | | | Methionine | 149 | G | | | | Phenylalanine | 165 | G | Aromatic | | | Tryptophan | 183 | G | | | | Praline | 115 | GK | | | | | | | **G = Glucogenic K = Ketogenic** | | ## C- Nutritional classification of Amino Acids: Amino acids could be classified into essential and non-essential amino acids. The essential A As are those which can not be synthesized or in-sufficiently synthesized by the body and they are required to be supplied in the diets, so they are called essential or indispensable amino acids. However, the amino acids that could be easily synthesized by the body though transamination of other amino acids or nitrogenous metabolites are called non-essential or dispensable A As. - There are 10 essential AAs for the non ruminants which are: - Arginine, Histidine, Isoleucine, leucine, lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine. - Also, there are 10 non essential AAs which are: - Alanine, Aspartic acid, Citrulline, Cystine, Glutamic acid, Glycine, Hydroxy-proline, Proline, Serine and Tyrosine. - For ruminants the microorganisms, which are common inhabitants in the rumen, can utilize any kind of nitrogenous substance present in the animal ration, and converts them into different essential and non-essential amino acids that are deposited as microbial protein and later on utilized by the animal body. Thus the essential amino acids required only in non-ruminants like man, pig, horse, poultry, etc. but not for sheep, goat or cattle except during their very young age when their rumen is not developed to carry this function. - Table (2) Requirement for each essential amino acid when all other amino acids of nutritive importance are adequate and provided for non ruminants as percentages of total diet | | Growing pig | Laying hen | Starting Chicken | Young rat | Amino acid | |-----------------|-------------|------------|------------------|-----------|----------------------| | | (1) | (1) | (1) | (1) | | | Arginine | 0.80 | 1.20 | 1.00 | 0.20 | | | Glycine | | | 0.40 | 0.30 | | | Histidine | | | | 0.30 | | | Isoleucine | 0.53 | 0.50 | 0.75 | 0.50 | | | Leucine | 0.64 | 1.2 | 1.10 | 0.50 | | | Lysine | 0.75 | 1.40 | 0.90 | 0.80 | | | Methionine | 0.52(2) | 0.52(2) | 0.75(2) | 0.60(2) | | | Phenylalanin | 0.52(4) | 0.80(3) | 1.30(3) | 0.90(3) | | | Threonine | 0.45 | 0.45 | 0.20 | 0.48 | | | Typtophann | | 0.55 | 0.70 | 0.15 | | | Valine | | | 0.58 | 0.70 | | | Total Protein | 16-18 | 17 | 23 | 20 | | - (1) Non essential - (2) About 1/3 of the requirement can be met by cystina. - (3) About 1/3 to 1/2 the requirement can be met by tyrosine - (4) About 1/3 of the requirement can be met by tyrosine ## Metabolism of Proteins: ### A. In Non-ruminants #### I. Protein digestion: Digestion of protein is the process by which protein is broken down to amino acids by successive action of the gastric, pancreatic and intestinal proteolytic secretions and enzymes. Specific enzymes hydrolyze the dietary proteins as shown in table (3) | Product of digestion | Substrate | Origin | Enzyme | |-----------------------|-----------------------------------------|-----------------------------------|----------------------------| | Clots of milit | Milk protein (casine) | Gastric mnca | Remin | | Polypeptides | Proteins & polypeptide | Gastrie mucose | Pepsto | | Peptides and A As | Proteins & polypeptide | Panceras | Trypsin | | Peptides and A As | Proteins & polypeptide | Panceras | Chymotrypsin | | Peptides and A As | Proteins & polypeptide | Panceras | Carboxy peptidase | | Peptides and AAs | Proteins & polypeptide | Panceras | Pre-elastase | | Peptides and AAs | Proteins & polypeptide | Small intestine | Amino peptidase | | Amino acids | Proteins & polypeptide | Small intestine | Dipeptidase | | Amino acids | Proteins & polypeptide | Small intestine | Tripeptidase | | Purine, Phosphoric | Nucleoprotein | Small intestine | Nucleotidaze | | acid and pentose's | Nucleoprotein | Small intestine | Nucleosidase | | Activating enzymes | Pancriatic and | Small intestine | Enterokinase | | | intestinal | Small intestine | Enteropeptidase | | | crude Enzymes | | | ## II.Absorption of the Amino Acids: Absorption of the A As takes place by active transport. The brush border membrane of the small intestine contains at least two active transport systems, one for the neutral amino acids and another for basic AAs. The AAs move across the intestinal cell membrane against a concentration gradient, requiring energy supplied by cellular metabolism. Some amino acids may compete with each other for transport. ## The excess of amino AAs are splited to amino group, which ends in the liver forming urea or uric acid which execrated through urine. While carboxylic group or keto acids are eventually oxidized to liprate energy, CO2 and H2O by the tricarboxylic acid cycle. Glycoproteins and lipoproteins also are metabolized through the tricarboxylic acid cycle. ## Factors affecting protein digestion: 1. **Age and species of the animals:** Digestion of protein differs according to age's species of the animals as follows: Young animals of all species shows lower protein digestibility than adult ones. And ruminants digest protein more efficient than non-ruminants. 2. **The nature of protein:** The protein of tendon, skin, hair, feather and hoofs are relatively indigestible. The digestion of plant proteins cannot be satisfactorily due to presence of high fiber content in relation to animal proteins.