For Nursing Students

1. Biochemistry
for
B.Sc.Nursing
ENZYMES
BRAINSTROMING NOTES TO PRINT

2.  Enzymes are defines as the bio-catalyst
synthesized by the living cells which increase
or decrease the rate of reaction in the living
organism.

3. • Are protein in nature.
• Are specific in action.
• Are required in very small amount.
• The loss of catalytic activity is observed when they
are subjected to heat or strong acids or bases or
organic solvent.
• The metabolic pathways are mainly catalyzed by
enzymes.
• Enzyme deficiency leads to inborn errors of
metabolism.
• Most of the enzymes are produced by the cells of a
particular tissue and function within that cell. Such
enzymes are called as intracellular enzymes.

4. • Almost all enzymes are proteins by nature.
• Enzymes with two or more subunits are called as oligomeric
enzymes.
• Several enzymes occurs in the form of the multienzyme
complex. E.g Pyruvate DH, Fatty acid synthase complex.

5.  According to the international Union of
Biochemistry (IUB) system . Enzymes are
classified into six major classes:
• Oxidoreductases
• Transferases
• Hydrolases
• Isomerase
• Lyases
• Ligases

6.  These catalyse oxidation reductions or
involved in oxidation-reduction reactions.
AH2+B=A+BH2
(Oxidation = Reduction)
e.g. Alcohol dehydrogenase,
Cytochrome oxidase,
L- and D-amino acid oxidase

7.  These enzymes catalyse the transfer of a
functional group from one substrate to
another.
A-X+B=A+B-X (Group transfer)
e.g. Hexokinase,
transaminases,
phosphorylase

8.  These enzymes bring about hydrolysis of
various compounds.
A-B + H2O =AH + BOH
(Hydrolysis)
e.g. Choline esterase,
acid and alkaline phosphatases,
pepsin,
urease

9.  These enzymes catalyse inter conversion of
optical, geometric or positional isomers.
A = A1
(Interconversion of isomers)
e.g. Retinol isomerase,
phosphohexose isomerase

10.  These enzymes catalyse removal of group
of mechanism other than hydrolysis.
A-B + X-Y = AX-BY
(Addition = Elimination)
e.g. Fumarase,
Histidase,
Aldolase

11.  The enzyme catalyse the synthetic
reactions where two molecules are joined
together and ATP is used.
A+B = A-B
(Condensation (Usually dependent on ATP)
e.g. Succinate thiokinase,
Glutamine synthetase,
Acetyl CoA carboxylase

12.  PH
 Temperature
 Concentration of Substrate
 Concentration of Enzymes

13.  Specific Enzyme activity is maximum at a specific
pH.
 Enzyme activity may decrease due to increase or
decrease in pH.
 E.g. Pepsin has opt. pH of 1-2.
 Amylase has opt. pH of 6.8.
 ALP has opt. pH of 9.0

14.  Enzyme activity is maximum at optimum
temperature.
 Drastic change in the optimum temperature
results in the loss of enzyme activity.

15.  Substrate is directly proportional to the
enzyme activity.

16.  Velocity of enzyme reaction is directly
proportional to the enzyme concentration.

17. Oligometric-enzymes:
Enzymes with two or more subunits.
Halo-enzymes:
Enzymes which requires the presence of certain
additional organic or inorganic substances and are
conjugated protein .
Apo-enzymes:
Protein part of the conjugated protein.
Prosthetic group:
Non protein part of the conjugated protein present
in haloenzymes.

18.  Co-enzyme:
 Are dialyzable, thermostable, low molecular weight organic
substances, which may be regarded as a co- or second substrate
required for the reaction to complete. E.g. NAD+ is required for the
activity of lactate dehydrogenase.
 Metallo-enzymes:
 Presence of metal as Mg2+ (for Hexokinase) with apoenzymes.
 Co-factor:
 Inorganic ions as Mg2+ present in the metallo-enzymes are co-factor.
 Iso-enzyme/Isozyme:
 Different form of the same enzyme catalysing the same reaction.
Isoenzymes are the physically distinct forms of the same enzymes but
catalyse the same chemical reactions and differ from each other
structurally, electrophoretically and immunologically. Eg. Lactate
Dehydrogenase (LDH), Alkaline Phosphatase (ALP), Creatine
Phosphokinase (CPK).

19.  The diagnostic enzymes are classified a/c
to the organ they belong:
 Liver Enzyme: AST, ALT, ALP & GGT
 Cardiac Enzyme: LDH, LD1, CK. CKMB, AST
 Muscle Enzyme: CK, LDH, AST
 Pancreatic Enzyme: Amylase, Lipase
 Bone Enzyme: ALP & ACP

20.  AST (Aspartate transminase)
 ALT (Alanine transminase)
 LDH (Lactate dehydrogenase)
 CK (Creatine kinase)
 ALP (Alkaline phosphatase)
 ACP (Acid phosphate)
 GGT (Gamma Glutamyl transferase)
 Amylase
 Lipase
 Cholinesterase
 Glucose 6 (P) DH

21. Thank You