Hydrolysis of glycosidic bond.
e.g. Amylase, Maltase, Sucrase, Lactase
LIPID HYDROLYZING ENZYMES
I. LIPASES act on TAG
II. CHOLESTERYL ESTERASE hydrolyze C – esters
III. PHOSPHOLIPASES act on PL
OTHER ESTER HYDROLYZING ENZYMES
e.g. Acid phosphatase , alkaline phosphatase
G-6-P + H2O Glucose + Phosphoric acid
Splits off one phosphate group of diesters.
Hydrolyze mononucleotides to nucleosides & H3PO4.
Nucleoside + H3PO4 free nitrogen base +
acetylcholine to acetic acid & Choline.
Catalyze hydrolysis of sulfate esters.
Catalyze addition of NH3, H2O, CO2 to double bond or
their removal from double bond.
│ fumarase │
CH + H2O HOCH
Fumaric acid Malic acid
Catalyze structural change within a single molecule by
transfer of group within it resulting in formation of an
isomeric form of the substrate.
Glucose-6-P Fructose 6-P
Catalyze condensation reactions joining two molecules by
forming C-O, C-S, C-N, C-C bonds along with energy
releasing hydrolysis or cleavage of high energy phosphates.
CH3 Acetyl CoA COOH
│ carboxylase │
C=O + CO2 +ATP CH2 + ADP + Pi
Acetyl CoA Malonyl CoA
Specific in their action though to a variable extent.
CO2 + H2O H2CO3
Pancreatic esterase; hydrolyze both aliphatic esters &
TRYPSIN; hydrolyze residue of only lysine & arginine.
LIPASES; hydrolyze ester bond.
one enzyme catalyze same reaction on a group of structurally
HEXOKINASE; catalyze Phosphorylation of
Enzymes distinguish b/w D-& L-sugars as well as D-& L-
2. PROTEIN NATURE
Enzymes are protein in nature
Except few RNAs
3. DIRECTION OF ENZYME REACTION
A + B C + D
A + B C + D
Inactive form of enzymes.
Active site of enzyme is masked by a small region of
peptide chain that is removed by hydrolysis of specific
Prevent autolysis of cellular structural proteins.
e.g. Pepsinogen ; pepsin by gastric HCL
Trypsinogen ; trypsin
Cytosol ; F.A synthesis
Mitochondria ; F.A oxidation
6.ENZYMES CATALYZING RATE - LIMITING
Enzyme catalytic efficiency determines efficiency of an entire
HMG-CoA reductase cholesterol synthesis
statin drugs inhibit it.
Enzymes previously absent or present only in traces in certain
microorganisms can be induced by substances called INDUCERS,
which in many cases are actual substrates.
e.g. Induction of penicillanase by penicillin in bacteria
Phenobarbitone induces synthesis of many hepatic
microsomal enzymes including bilirubin glucuronyl
Barbiturates ↑ δ ALA synthetase & precipitates acute
INSULIN induces enzymes of glycolysis
GLUCAGON represses them
E.COLI make tryptophan synthetase when medium
doesn't contain tryptophan.
Physically distinct version of a given enzyme, each of which
catalyze the same reaction.
LDH , 5 isozymes
LDH I HHHH (heart)
LDH 2 HHHM
LDH5 MMMM (muscles)
CK , 3 isozymes
CK 1 BB (brain)
CK 2 BM (heart)
CK 3 MM (sk. Muscles)
DIAGNOSIS OF MI
Regulatory proteins involved in myocardial contractility.
Troponin I & Troponin T
Enzymes of diagnostic importance
DIAGNOSIS OF MI
ENZYME TIME OF
PEAK LEVEL DURATION OF
TROPONIN I 4-6 hr 8-24 hr 3-10days
CK-MB 4-8hr 12-24hr 48-72hr
AST 6-8hr 24-48hr 3-5days
LDH 12-24hr 48-72hr 7-12days