Isoenzymes


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Isoenzymes

 

isozymes, different structural forms of enzymes with a single type of catalytic activity in organisms of the same species (or tissue).

Isoenzymes catalyze the same reaction but differ in amino acid composition and in some of their physical, immunological, and catalytic properties. Isoenzymes consist of several polypeptide chains (subunits), combined in various ways to form a quaternary enzyme structure. Thus, two forms of the lactate dehydrogenase enzyme are found in the chick—one characteristic of skeletal muscles, the other of heart muscle. In all, five isoforms of this enzyme have been found in chicks and other organisms, each form (tetramer) made up of four protein subunits of two types. Electrophoresis can be used to separate isoenzymes. In organisms of the same species (or in the same tissue), isoenzymes form a characteristic set, or spectrum, which may be altered with pathological tissue changes (useful in diagnosis) and in the process of ontogeny.

REFERENCES

Wilkinson, G. Izofermenty. Moscow, 1968. (Translated from the English.)

E. V. PETUSHKOVA

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QPCTL is an isoenzyme of QPCT and can be inhibited by Vivoryon's lead candidate small molecule PQ912 and other compounds protected under Vivoryon's patents.
Serum lactate dehydrogenase isoenzyme and total lactate dehydrogenase values in health and disease, and clinical evaluation of these test by means of discriminant analysis.
In healthy adults, the greatest part of serum ALP levels is constituted from liver and bone isoenzymes, whereas the majority of serum ALP is bone-derived in children as a result of growth.
Deficiencies of N-acetyl-[beta]-hexosaminidase A and B isoenzyme activities in neonatal body are the reason for storing gangliosides in their lysosomes that cause Sandhoff and Tay-Sachs diseases [11].
Isoenzymes were resolved on 8% alkaline native polyacrylamide gel system with 4% stacking gel (Davis, 1964) at 4AdegC using a Bio-Rad protean II electrophoresis unit running at constant current of 30 amps per gel with voltage set at maximum.
[1,5] At present, creatine kinase-MB isoenzyme (CKMB), MB and cardiac troponins T and I (cTnI & cTnT) are used in the diagnosis of AMI.
In addition to increased absorption, piperine seems to be a non-specific general inhibitor of CYP isoenzymes; IV phenytoin levels also were higher among test participants.
Only one esterase band, EST0.20, in both types of cysts was observed in the esterase isoenzyme pattern; the esterase in the white cysts showed a darker band and exhibited more activity than the esterase in the brown cysts.
Objective: To determine the levels of serum lactate dehydrogenase 2 (LD2) Isoenzyme and b2 microglobulin (b2m) in patients of non-Hodgkin's lymphoma (NHL) and to correlate these levels in NHL patients with and without bone marrow infiltration.
To date, about 16 CA isoenzymes responsible for various functions have been identified.
Although both COX isoenzymes catalyze the oxygenation of arachidonate, COX-2 shows a more diverse substrate selectivity compared to COX-1.