ENZYMES 1 Dr AQSA MALIK ENZYMES Biological catalysts
ENZYMES - 1 Dr. AQSA MALIK
ENZYMES Biological catalysts which speed up the rate of reaction without becoming part of the reaction but themselves cannot initiate any chemical reaction.
CLASSIFICATION OF ENZYMES Formulated by the enzyme commission of IUB. Six major classes based on the type of reaction catalysed. 1. OXIDOREDUCTASES Catalyzing oxidation reduction reactions. 2. TRANSFERASES Catalyzing group transfer e. g Phosphate, amino, acyl and methyl
3. HYDROLASES Catalyzing hydrolytic breakdown, add water molecules to substrate which is decomposed 4. LYASES Catalyzing removal of groups by mechanism other than hydrolysis and leaving behind double bonds.
5. ISOMERASES Catalyzing interconversion of isomers. 6. LIGASES Catalyzing formation of bonds and new compounds.
1. OXIDOREDUCTASES OXIDASES. Catalyzing oxidation and atomic oxygen is added to the hydrogen removed from the substrate forming H 2 O or H 2 O 2 O₂ + H₂O___ H 2 O 2 hypoxanthine oxidase
DEHYDROGENASES. Catalyzing removal of hydrogen from substrate but are not able to use oxygen as hydrogen acceptor, removed hydrogen atoms are taken up by special acceptors such as NAD, NADP , FAD___ FADH 2 Succinic acid fumaric acid succinate dehydrogenase
HYDROPEROXIDASE two enzymes in this class peroxidase and catalase catalize the decomposition of H 2 O 2 catalase 2 H 2 O 2 2 H 2 O +O 2 peroxidase H 2 O 2+2 H+2 e- ______ 2 H 2 O
OXYGENASES. Catalysing oxidation of the substrate and oxygen is added to the substrate e. g O 2___ H 2 O phenylalanine _____ tyrosine phenylalanine hydroxylase
2. TRANSFERASES TRANSAMINASES Catalyzing transfer of amino group between an aminoacid and a ketoacid e. g alanine transaminase. ALT Glutamic acid+Pyruvic acid alpha ketoglutaric acid+Alanine
TRANSFERASES TRANSMETHYLASES. Catalyzing transfer of methyl group e. g COMT Noradrenalin+CH₃ Adrenaline
TRANSFERASES TRANSPEPTIDASES. Catalyzing transfer of aminoacids to substrates. benzoyl co. A +glycine ____ hippuric acid PHOSPHOTRANSFERASES. Catalyzing transfer of phosphate group to substrate e. g Hexokinase, glucokinase. TRANSACYLASE. Catalyzing transfer of acyl groups to substrates e. g Choline acetyltransferase.
3. HYDROLASES Catalyzing hydrolytic breakdown of different bonds. Most of the GIT enzymes belong to this class.
HYDROLASES a. ENZYMES HYDROLYZING CARBOHYDRATES. Polysaccharidases STARCH AMYLASE MALTOSE+MALTOTRIOSE Oligosaccharidases DEXTRINASE GLUCOSE Disacharidases SUCROSE SUCRASE FRUCTOSE+GLUCOSE
HYDROLASES b. ENZYMES HYDROLYZING LIPIDS. Lipases Pancreatic lipase Esterases Cholesterol esterases Phospholipases
HYDROLASES c. ENZYMES ACTING ON PEPTIDE BONDS. Exopeptidases polypeptidase Tripeptidase Dipeptidase Endopeptidase e. g pepsin
HYDROLASES d. PHOSPHATASES. Phosphomonoesterases Phosphodiesterases Phosphorylases Pyrophosphatase Nucleases Nucleotidases nucleosidases
HYDROLASES e. deaminases f. deamidases
4. LYASES Catalyzing reactions in which groups are removed without hydrolysis leaving a double bond or add groups to already existing double bonds. Pyruvate decarboxylase Pyruvate Acetaldehyde
5. ISOMERASES Involved in the interconversion of pair of isomeric compounds. Glucose 6. P isomerase fructose 6. P
6. LIGASES Catalyzing reactions in which linking together of two molecules occur coupled with the breakdown of a high energy phosphate bonds. Acetyl. Co. A+ATP malonyl Co. A Acetyl Co. A carboxylase
THANK YOU
- Slides: 23