Multiple Forms of Enzymes

Enzyme Nomenclature. Recommendations (1992) Academic Press, New York Nomenclature of multiple forms of enzymes J. Biol Chem. (1977) 252, 5939-5941 Catalytic activity Units of enzyme activity Eur. J. Biochem. (1979) 97, 319-320 Symbolism and terminology in enzyme kinetics Eur. J. Biochem. (1982) 128, 281-291... 

Nomenclature of Multiple Forms of Enzymes hitp//ww vv.cliem.qmul.ac.uk/iubmb /misc/isoen.html... 

In mammalian cells, there are multiple forms of enzymes within the same family, e.g., protein kinase C, phospholipase C, and caspase. A selective assay system would be instrumental in such cases to advance understanding of the respective role for each form within the same enzyme family. An example for design of a selective assay system for the superfamily of phospholipase A2 is provided in this chapter. Such a selective assay system may play a signihcant enabling role for PLA2 and other enzyme families in the discovery of inhibitors relevant to the treatment of pathologies involving those enzymes. 

Figure 8-2 Nongenetic modifications that may give rise to multiple forms of enzymes. (From A4oss DW. Isoenzymes. London, Chapman Hall, 1982.)...

Distribution of Isoenzymes and Other Multiple Forms of Enzymes... 

Commission on Biochemical Nomenclature. L Nomenclature of multiple forms of enzymes. J Biol Chem 1977 252 5939-41. 

Isoenzymes and multiple forms of enzymes may provide additional organ specificity. Table 23-6 summarizes various enzymes, their associated types of malignancy, and the assays used to measure their activity (Act) or their mass concentration (RIA or immunometric assay). Enzymes are traditionally measured by their activities. With the introduction of antibody techniques, some enzymes, such as PSA, are measured as protein antigens rather than by their enzyme activity. 

M8. Markert, C. L., and Moller, F., Multiple forms of enzymes Tissue, ontogenetic and species specific patterns. Proc. Natl. Acad. Sci. V.S. 46, 753-763 (1959). 

Multiple Forms of Enzymes. Isozymes, or isoenzymes, provide an avenue for varying regulation of the same reaction at distinct locations or times. Isozymes are homologous enzymes within a single organism that catalyze the same reaction but differ slightly in structure and more obviously... 

Most workers have adopted the international convention on nomenclature of multiple forms of enzymes (12), so that the major isoenzymes of cholinesterase are numbered consecutively, with the form having the highest mobility towards the anode being designated one. Unfortunately, there are two sets of symbols for the electrophoretic bands of the enzyme, namely C1-C4 (H6) and ChEj-ChEs e.T (L8). It turns out that C1-C3 are identical to ChEj-ChEs, respectively, but C4 is identified with ChE4 +... 

In order to understand the selective toxicity of drugs such as PM and TM, and their significant differential activity between protozoa and bacteria, a brief discussion of multiple forms of enzymes is in order. 

Initially, the concept of isoenzymes had only an operational character (Markert, 1968). Isoenzymes (isozymes) were considered to be any multiple fraction of the same enzyme (Shaw, 1969 Serov, 1968). But later, with the collection of various experimental data, this concept acquired a genetic meaning, and after this the concept of isozymes was given to the genetically determined variants of the same enzyme in the same organisms, as characterized by their similar substrate specificity. The Nomenclature of Multiple Forms of Enzymes, 1971) Enzyme fractions which were not genetically determined were termed multiple forms of enzymes. 

Isoenzymes are enzymes having the same function but differing somewhat in structure. The existence of isoenzymes, isozymes, or also multiple forms of enzymes has been known for some time. However, it was not until zone electrophoresis on suitable supports provided a method of separation that it could be shown that isozymes are of almost universal distribution. 

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