Class of enz lec 4
- 2. Classification of Enzymes According to the International Union of Biochemistry or Biochemists Enzymes are classified into SIX major classes
- 3. Class I – Oxidoreductases, catalyze oxidation reductions Class II – Transferases Catalyzing group transfer Class III– Hydrolases Catalyzing hydrolysis Class IV– Lyases Catalyzing addition of groups to ═ bonds Class V -- Isomerases Catalyzing isomerization Class VI – Ligases Catalyzing condensations
- 4. I Oxidoreductases They catalyze oxidation and reduction reaction. These enzymes are divided into three groups.
- 5. (a) Oxidases: Those which use oxygen as hydrogen as acceptor eg:- L amino acid oxidases. L a.a + H2O + O2 2 oxoacids + NH3+H2O2 Eg: D-amino acid oxidases, Tyrosinase,Cyt-oxidases, Uricases.
- 6. (b) Anaerobic Dehydrogenases Those which use some other substances as Hydrogen acceptor , eg: NAD,NADP Enz: 1) Malate Dehydrogenase 2) Succinate Dehydrogenase 3) Lactate Dehydrogenase.
- 7. These anaerobic dehydrogenases can further be sub-classified as (i) Those acting on CH-OH of donors eg: Glycero-P-dehydrogenase Gly-3-P + NAD ═ Di Hydroxy Acetone P + NADH Other eg:-- lactate Dehydrogenase Malate Dehydrogenase Isocitrate Dehydrogenase
- 8. (ii)Those acting on CH-CH group of donors eg: Dihydrouracil dehydrogenase 4,5 dihydrouracil + NAD+ ═ Uracil + NADH (iii) Those acting on CH-NH2 group of donor with NAD or NADP as acceptor. eg: Glutamate Dehydrogenase Glutamate + H2O + NAD+ ═ 2 oxoglutarate NH3 + NADH
- 9. (C) Hydroperoxidases Acting on H2O2 as acceptor, or those which use hydrogen peroxide as substrate. eg:Catalase , Peroxidase H2O2 + H2O2 ══ O2 +2H2O
- 10. II Transferases They catalyze the transfer of some groups from one molecule to the other. (1) Methyl Transfer: Methyl transferases a. S-adenosyl Methionine + Guanidino acetate ║Guanidino acetate Methyl transferase S-adenosyl homocysteine + Creatine b. Serine hydroxy methyl transferase Serine Glycine
- 11. (2)Carboxl transfer-- eg: Aspartate Transcarbamylase (3) Aldehyde, Keto Residue Transfer--eg: Transaldolase, Transketolase (4) Glucosyl Transfer--eg: Transglucosylase (5)Amino Grp Transfer--eg: Transaminases (6) Phosphorus Transfer eg: Glucokinases,Hexokinases (7) Transfering Sulphur-- eg: Trans-sulfurase (8) Acyl Transferases—eg:Transacylases
- 12. III Hydrolases They catalyze the hydrolysis of substrate by addition of water molecule across the bond which they split
- 13. (I) Acting on Ester bonds-Esterases • (a) Acetylcholine-esterase Acetylcholine +H2O Choline + Acetic Acid • (b) Alkaline Phosphatase Orthophosphoric mono ester+H2O an Alcohol +H3PO4 Eg: G-6-P + H2O D glucose + H3PO4
- 14. (ii) Acting on Glycosyl compound • Amylases β galactosidases (iii) Acting on Peptide bonds • Peptidases aminopeptidases,carboxypeptidases (iv)Acting on C-N bonds • Deamidases Urease (Urea Amido Hydrolase) Eg: Urea + H2O = CO2 + 2 NH3
- 15. (v) Acting on Acid Anhydride bonds (a)Pyrophosphate Phosphorylase (Synthetic Name) • This enzyme is also called Inorganic pyro phosphatase (trivial name) • Pyro PO4 + H2O == 2 ortho phosphate (b)ATP Phospho Hydrolase (synthetic name) • ATP ase (trivial name) • ATP + H2O == ADP + orthophosphate
- 16. IV .Lyases •They catalyze the splitting of group from substrate without hydrolysis or oxidation,reduction.
- 17. (i) C-C Lyases : Pyruvate Decarboxylase 2 oxo acids == an Acid + CO2 (ii) Keto Acid Lyase : Isocitrate Lyase Citrate + CoA = Acetyl CoA + H2O +oxalo acetate (iii) C-oxylyase : Serine Hydrolyase or Serine Hydratase Serine + H2O == Pyruvic + NH3 + H2O Acid
- 18. V Isomerases • They catalyze isomeric conversions or epimeric conversions. • Eg: Isomerases,Racemases, Epimerases
- 19. VI- Ligases (i) Tyrosine S RNA Ligase or Tyrosyl RNA Synthetase. ATP + Tyr. + RNA ═ AMP + Pyr PO4 + Tyrosyl S RNA (ii) CTP Synthetase (iii) GMP Synthetase.
- 20. Ligases can join or form • C-O bonds Tyrosyl S. RNA Synthetase Leucyl S.RNA Synthetase Alanyl S.RNA Synthetase • C-N bonds GMP Synthetase CTP Synthetase
- 21. • C-C bonds (i) Pyruvate CO2 Ligase or Pyruvate Carboxylase ATP +Pyruvate +CO2 + H2O = ADP +Oxaloacetate + Ortho P (ii) Acetyl CoA CO2 Ligase or Acetyl CoA Carboxylase • ATP + Acetyl CoA + CO2 + H2O ║ ADP + Ortho P + Malonyl CoA