Isoenzymes of NAD and NADP Dependent Dehydrogenases

Abstract

Publisher Summary This chapter focuses on isoenzymes of NAD and NADP dependent dehydrogenases. The first description of a real isoenzyme concerned a dehydrogenase. In a study, two forms of lactate dehydrogenase (LDH) were isolated having strong differences in the biochemical and physical properties. To examine the structure and function of dehydrogenases or other isoenzymes, three conditions must be fulfilled: (i) Different biochemical and physical characteristics associated with the same qualitative substrate specificity and a similar molecular weight; (ii) Different distribution patterns of an isoenzyme mixture in different functional organs or tissues. In the case of microorganisms, distinct distribution patterns appear under different metabolic conditions; (iii) Different genetic control of the basic isoenzyme types, which can result in the occurrence of intermediate types by the process of hybridization. With these conditions in mind, the discussion of the isoenzyme problem can be determined. In this chapter, structure of dehydrogenase isoenzymes is discussed in detail. Structure of LDH from pig heart and pig muscle is described. Function of the LDH isoenzymes is elaborated. An overview of cytoplasmic and mitochondrial malate dehydrogenase (MDH) is also presented.