Coupon Accepted Successfully!



Isoenzymes are different molecular forms of enzymes that may be isolated from the same or different tissues e.g. LDH1, LDH2, LDH3, LDH4, LDH5. All the properties of different Isoenzymes are different like Km , Vmax, electrophoretic etc, EXCEPT the reaction catalysed.


  1. Enzyme Activities Useful in Clinical Diagnosis

Assayed Enzyme

Diagnostic Uses

Acid phosphatase

Prostate cancer

Alanine aminotransferase

Viral hepatitis, liver damage

Alkaline phosphatase

Liver disease, bone disorders


Acute pancreatitis

Creatine kinase

Muscle disorders, heart attack

Lactate dehydrogenase

Heart attack

  1. Recent Advances: Involvement of Serine proteases in tumor cell metastasis
    The serine protease urokinase plasminogen activator is believed to be required for metastasis of cancer cells. Metastasis is the process by which a cancer cell leaves a primary tumor and migrates through the blood or lymph systems co another tissue or organ, where a secondary ­tumor grows. Increased synthesis of urokinase-type plasminogen activator (uPA) has been correlated with an increased ability to metastasize ­in many cancer. uPA activates plasminogen to form plasmin. Plasminogen is ubiquitously located in the extracellular space and its activation to plasmin can cause degradation of proteins in the extracellular matrix through which the metastasizing tumor cells migrate. Plasmin can also convert procollagenase to collagenase, which promotes degradation of collagen in the basement membrane surrounding the capillaries and lymph system. This promotion of proteolytic activity by uPA secreted by tumor cells or stromal cells in the environment of tumor cells allows tumor cells to degrade the extracellular matrix pro­teins and invade through the matrix to form secondary tumor sites.
  2. NADPH Oxidase (NOX) in health and disease.  
    1. The discovery and characterization of NADPH-dependent oxidase (NOX) in phagocytic cells had suggested that this tissue was the sole location of NOX in the body, where its physiological role was to produce ­large amounts of superoxide to kill microbes.
    2. Elucidation of the biochemical properties of phagocytic NOX also benefited from stud­ies of patients with chronic granulomatous disease, which presents as an inability of affected individuals to combat infection resulting from mutation in NOX, which lead to loss of ability to produce adequate amounts of superoxide.
Vitamin Coenzyme Function as coenzyme Entity Transferred
Thiamine (vit B1)
Thiamine pyrophosphate (TPP) Oxidative decarboxylation and transketolase reaction Hydroxy-ethy1
Riboflavin (vit B2) Flavin adeninedinucleotide (FAD) and flavin mononucleotide (FMN) Oxidation and reduction reaction Hydrogen atoms
Niacin Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP+) Oxidation and reduction reaction Hydride ion (H-)
Pyridoxin (vit B6) Pyridoxal phosphate (PLP) Transamination,deamination,
Decarboxylation of amino
Amino group
Biotin Biocytin Carboxylation reaction Carbon dioxide
Folic acid Tetrahydrofolate (THF) Carrier of one carbon group
(other than co2)
One carbon group
Pantothenic acid Coenzyme A Acyl carrier Acyl group
Cyanocobalamin Methylcobalamin    

Ca+2 Lipase, Lecithinase
Copper (Cu+2/Cu+) Cytochrome oxidase, Tyrosinase, Lysyloxidase, Superoxide dismutase, Ascorbic acid oxidase, Ferroxidase (Ceruloplasmin)
Iron (Fe+2 / Fe+3) Cytochrome oxidase, Xanthine oxidase, Catalase, Peroxidase
Zine (Zn=2)
Carbonic anhydrase, alkaline phosphatase, RNA polymerase, alcohol dehydrogenase, Carboxypeptidase, Porphobilinogen synthase, glutamate dehydrogenase, lactate dehydrogenase, Superoxide dismutase
Magnesum (Mg+2) Hexokinase, phosphofructokinase, glucose-6-phosphatase, enolase, creatinine kinase, Phosphatases, Kinase.
Maganese (Mn+2)  
Arginase, Pyruvate carboxylase, phosphoglucomutase, Glycosyl transferase, Hexokinase, Enolase.
Potasium (K+) Pyruvate kinase
Selenium Glutathione peroxidase
Nickle (Ni+2) Urease
Molybdenum Xanthine oxidase
Note : Some metalloenzymes contain more than one metal e.g. cytochrome oxidase contains both iron and copper.

Suicide inhibitors:  
  1. These compounds are relatively uncreative until they bind to the active site of a specific enzyme. On binding to the active size of the enzyme they carry out the first few catalytic activities of the normal enzyme reaction. Instead of being transformed into a normal product,
  2. The inhibitor is converted to a very reactive compound that combines covalently with the enzyme leading to its irreversible inhibition.
  3. So enzyme literally commits suicide by converting inhibitor into reactive compound. Allopurinol is a suicide inhibitor of xanthine oxidase.

Test Your Skills Now!
Take a Quiz now
Reviewer Name