Protein Types PDF

Protein types  Prof / Ayman El Baz Professor of Medical Biochemistry & Molecular Biology Dr/ Sara El Derbaly Assistant Professor of Medical Biochemistry & Molecular Biology ❖ By the end of this lecture, the students should be able to: 1. List the biologica...

Protein types  Prof / Ayman El Baz Professor of Medical Biochemistry & Molecular Biology Dr/ Sara El Derbaly Assistant Professor of Medical Biochemistry & Molecular Biology ❖ By the end of this lecture, the students should be able to: 1. List the biological importance of proteins 2. Describe the general structure of proteins 3. Classify proteins  Protein 1. Definition 2. Biological importance 3. Classification 1.Definition & general structure of Proteins Proteins are: ❖Organic complex nitrogenous compounds ❖ Formed of C,H,O,N (+/- Sulfer) ❖Formed by polymers of amino acids= polypeptides chains ❖The amino acids are connected together by peptide link (-CO- Peptide link NH-) (where COOH group of the 1st AA unites with the NH2 group of the 2nd AA and so on) ❖ Ends of the polypeptide chain: ✓ COOH group: at one end → called C-terminal ✓ NH2 group: at the other end → called N-terminal 2.Biological importance of Proteins 1. Enzymes 2. Hormones (protein hormones) 3. Plasma proteins 4. Immunoglobulins (antibodies) 5. Receptors 6. Hemoglobin 7. Lipoproteins 8. Supporting structure (cartilage, bone, skin, nail, hair, etc) 3.Classification of protein Classification of proteins Conjugated Simple proteins (compound) Derived proteins proteins Product of Formed only Formed from hydrolysis of of amino protein + non simple or acids protein part compound proteins  A) Simple proteins Definition: They are proteins that on hydrolysis give only amino acids Types: Albumin, Globulin, Histone, Protamine, Glutelin, Gliadin, and Albuminoids (7): Albumin Globulin Histone Albuminoids (scleroproteins) (4 not) Keratin Collagen 1. Egg: egg albumin 1. Egg :egg globulin 1. Basic proteins rich Hair, nail Skin, cartilage 2. milk: lactalbumin 2. milk : lactoglobulin. in basic AAs Connective tissue 3. Blood :serum albumin 3. Blood: serum globulin 2. Present with nucleic Tendon, bones acid for packing in nucleosomes Coagulated by heat Not Coagulated by (4 NOT) Coagulation= change in the structure of protein heat Not coagulated by heat (from a liquid form to solid or a thicker liquid) Not digested by enzymes Not soluble in water Not in plant Supportive, protective function Gelatin** Gelatin** ✓ Obtained from collagen by boiling ✓ Forming gel by cooling ✓ Easily digested ✓ It is not adequate diet (low biological value)( deficient in some AA as tryptophan). Biological value of protein: High biological value proteins: They contain all the essential amino acids e.g. casein of milk, albumin and globulin. Low biological value proteins: They lack one or more essential amino acids e.g. gelatin, gliadin and vegetable proteins. B) Conjugated (Compound) protein Definition: They are protein conjugated with non-protein part (other groups) Types of conjugated proteins :(6) Types Non protein part Example Function 1. Glycoproteins Carbohydrates a. Hormones (FSH,LH) b. Antibodies c. Blood groups antigens (A,B) d. Receptors e. Enzymes 2. Lipoproteins Lipid Chylomicrons, VLDL, LDL& HDL Lipid transport in blood 3. Phosphoproteins Phosphoric acids Caseinogen main protein of milk 4. Metalloproteins Metals a. Ceruloplasmin (Cu) a- Carry & store copper (Cu) Cu, Fe, Zn b. Transferrin (Fe+2) b- Iron transport c. Ferritin ( Fe+3) c- Storage of iron d. Insulin ( Zn ) d- Regulation of blood glucose 5. Chromoproteins Pigment 1-Hemoproteins (heme ring) 1-Hemoglobin (HB), myoglobin 1-HB and myoglobin: O2 transport 2- FAD/FMN containing enzymes 2- Reducing equivalent (hydrogen 2-Flavoproteins (Flavin yellow carrier) pigment) 6. Nucleoproteins Nucleic acids -Chromosome (Histone protein+ DNA) 1- DNA -Ribosome (protein + RNA) 2- RNA C) Derived protein Definition: These are the denaturated or hydrolytic products of simple or conjugated proteins. Types of derived proteins: 1- Primary protein derivatives 2- Secondary protein derivatives 1. Definition They are products of protein They are products of progressive protein hydrolysis denaturation 2. Produced by Action of denaturing agents on protein Action of hydrolyzing agents on protein (eg. Heat or acid denaturation) (eg. Enzymatic hydrolysis) 3. Peptide bond No peptide bond break Peptide bonds break (no change in molecular weight (MW)) (decrease in molecular weight) 4. Example 1. Coagulated albumin 1. Proteose 2. Coagulated globulin 2. peptone 3. peptide 4. Amino acids  eg. coagulated albumin 1ry proteins derivatives 2ry proteins derivatives  References ▪ Vasudevan's Textbook of Biochemistry For Medical Students, 7th Edition. ▪ Chatterjea’s Textbook of Medical Biochemistry, 8th edition. ▪ Lippincott’s Illustrated Reviews: Biochemistry, 8th edition ▪