Enzymology: Properties & Classification Dr. Rohini C Sane

EnzymesDefinition of enzyme: Biocatalysts synthesized by living cells

Properties of Enzymes

1. Protein in nature (exception RNA ribosomes )

2. Colloidal & thermo labile

3. Specific in action

4. Hydrolysis of enzymes (proteins )

With strong acids With Enzymes

100 ⁰ C 37 ⁰ C

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EnzymesHistory of Enzymes :

1. 1876 Kuhnefound enzyme in yeast

2.1883 Buchner yeast ( sugar alcohol )

Isolation of enzyme system from cell free extract of yeast ( Zymase )

3.1926 :James Sumner

Isolation & crystallization of urease

4.1930 : Northtop

Crystallization of GIT enzymes

Nomenclature & classification of enzymes• I -Intracellular enzymes = nonfunctional plasma enzymes

• II –Extracellular enzymes = functional plasma enzymes—DIGESTIVE ENZYMES

IUB –International Union of Biochemistry enzyme commission 1961

Enzyme name = substrate + ase

substrate

E1 ↙ E2 ↓ ↘ E3 ↘ E4

Oxidation isomerization hydrolysis transfer

E1,E2, E3,E4 DIFFERENT ENZYMES WITH SINGLE ENZYMES

enzymes

↙ ↓ ↘ ↘

Substrate 1 Substrate 2 Substrate 3 Substrate 4

E SINGLE ENZYMES DIFFERENT NAMES

Classification of enzymes( IUB )EC Enzyme code number 4 digits

a) First digit main class type of reactions

b) Second digit subclass type of group involved

c) Third digit sub subclass type of substrate on which enzyme on which enzyme acts

d) Forth digit individual enzyme systematic serial number & name

Six Classes Of Enzymes

1. Oxido- reductases O

2. Transferases T

3. Hydrolases H

4. Lyases L

5. Isomerases I

6. Ligases L

Classification of enzymes1.Oxido reductases: catalyze oxidation of one substrate with simultaneous reduction of another substrate

EC 1.1.1.49 : G-6-P + NADP⁺ 6- Gluconolactone + NADPH+ H⁺

2. Transferase :catalyze Transfer of one group ( other than H )

EC 2.7.1.1 : Hexose + ATP * Hexose -6-P +ADP (* Hexokinase )

3. Hydrolase : catalyze hydrolysis of esters ,ethers ,peptides ,glycosides bonds by adding H2O & then breaking bonds

EC 3.1.1.7 : Acetyl Choline + H2O * Choline + Acetate(*Acetyl Choline Esterase –Hydrolase )

Classification of enzymes4. Lyases : remove groups from substrate or break bonds by mechanism other than hydrolysis

EC 4.2.1.2 : F 1,6 biphosphate * GAP+ DHAP ( *ALDOLASE )

5. Isomerases : produce optical, geometric isomers (racemase /epimerase/cistrans isomerase )

6. ligases :ATP dependent condensation of two molecules

Enzymes link substrate together usually with simultaneous hydrolysis of ATP

A+ B +ATP AB + ADP + Pi

• Glutamate + NH3 +ATP * Glutamine +ADP + Pi (* Glutamine Synthtase )

Classification of enzymes

CLASS CATALYSIS TYPE OF REACTION EXAMPLE

1 Oxido reductases Transfer of hydrogen Oxidation reduction AH2 +B A+ BH2

2 Transferase Transfer of groups other than H A-X +B A+B-X

3 Hydrolases Cleave bond after adding H2O Hydrolysis A-B +H20 AH +BOH

4 Lyases Cleave without adding H2O Lysis A-B +X-Y AX +B-Y

5 Isomerases Intramolecular transfer isomerization (A A’ )

6 Ligases ATP condensation of two molecules Ligation A+ B+ATP A-B +ADP +Pi

SynthatsesATP dependent biosynthetic reactionsGlutamine Synthtase

Synthase : ATP independent biosynthetic reactions ALA -Synthase ,GLYCOGEN Synthase

1.Oxido reductasesREDUCTION

Pyruvate + NADH Lactate + NAD⁺ ( Lactate Dehydrogenase )

←←←←

OXIDATION

Pyruvate & Lactate ( REDOX PAIR)

OXIDATION

Succinate +FAD⁺Fumarate + FADH +H( Succinate Dehydrogenase )

←←←←

REDUCTION

1.Oxido reductases

2. Transferases : Serum Glutamate Oxaloacetate Transaminase(SGOT)

2.Transferases : Serum Glutamate Pyruvate Transaminase (SGPT )

3.HYDROLASES

HYDROLASES : INVERTASE

3.HYDROLASES

4.LYASES

4.ISOMERASES :

6.Ligases

Naming of EnzymeENZYME NAME: 4 DIGIT NUMBER + SYSTEMATIC NAME

ATP + Glucose ADP + D- Glucose- 6- Phosphate

2.7.1.1 ATP Glucose Phosphotransferase

2 : Transferase (type of reaction)

1: Phospho transferase (type of group transferred )

1 : Hydroxyl group as acceptor (acceptor group )

1: Glucose as acceptor ( substrate )

TRIVIAL NAME :HEXOKINASE