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In biochemistry, isozymes (also known as isoenzymes or more generally as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. Isozymes usually have different kinetic parameters (e.g. different K M values), or are regulated differently.
AST exists in two isoenzymes namely mitochondrial form and cytoplasmic form. It is found in highest concentration in the liver, followed by heart, muscle, kidney, brain, pancreas, and lungs. [ 10 ] This wide range of AST containing organs makes it a relatively less specific indicator of liver damage compared to ALT.
Glycogen phosphorylase isoenzyme BB: 0.854 and 0.767 [12] 7 hours Glycogen phosphorylase isoenzyme BB (abbreviation: GPBB) is one of the three isoforms of glycogen phosphorylase. This isoform of the enzyme exists in cardiac (heart) and brain tissue. Because of the blood–brain barrier, GP-BB can be seen as being specific to heart muscle.
The Regan isoenzyme [clarification needed] [13] is one of the best studied [clarification needed] of these isoenzymes that is linked to several human cancers. Basically, the Regan isozenzyme is an alkaline phosphatase that is located in the placenta and associated with gonadal and urologic cancers.
Nitric oxide is mediated in mammals by the calcium-calmodulin controlled isoenzymes eNOS (endothelial NOS) and nNOS (neuronal NOS). [2] The inducible isoform, iNOS, involved in immune response, binds calmodulin at physiologically relevant concentrations, and produces NO as an immune defense mechanism, as NO is a free radical with an unpaired ...
The antioxidant enzyme glutathione peroxidase 4 (GPX4) belongs to the family of glutathione peroxidases, which consists of 8 known mammalian isoenzymes (GPX1–8).GPX4 catalyzes the reduction of hydrogen peroxide, organic hydroperoxides, and lipid peroxides at the expense of reduced glutathione and functions in the protection of cells against oxidative stress.
Hexokinase II/B constitutes the principal regulated isoenzyme in many cell types and is increased in many cancers. It is the hexokinase found in muscle and heart. Hexokinase II is also located at the mitochondria outer membrane so it can have direct access to ATP. [ 7 ]
More than five transcript variants encoding four active isoenzymes have been identified for this gene, however, not all variants have been fully described. The characterized isoenzymes have distinctive biochemical characteristics and substrate specificities, suggesting the existence of additional levels of complexity in polyamine catabolism.