PMID: 6411649Jan 1, 1983Paper

Lactate dehydrogenase A-subunit and B-subunit deficiencies: comparison of the physiological roles of LDH isozymes

Isozymes
T KannoY Nishimura

Abstract

Different clinical features exist for lactate dehydrogenase A-subunit and B-subunit deficiencies. The metabolic basis for these clinical differences was elucidated by investigating carbohydrate metabolism in the affected tissues. Glycolysis was markedly retarded at the position of glyceraldehyde 3-phosphate dehydrogenase, and significant increases of glyceraldehyde 3-phosphate, dihydroxyacetone phosphate, and fructose 1,6-diphosphate were observed. The physical and kinetic properties of glyceraldehyde 3-phosphate dehydrogenase prepared from human erythrocytes and skeletal muscle were almost identical, but the mode of inhibition of the enzyme was slightly different in erythrocytes and in skeletal muscle. In erythrocytes, impaired reoxidation of NADH followed by the deficiency of substrate NAD+ causes a reduction of glyceraldehyde 3-phosphate dehydrogenase activity. However, in skeletal muscle, the increased level of NADH markedly inhibits the enzyme under anaerobic conditions. A flux of triose phosphates from glycolysis occurred in skeletal muscle of a patient with A-subunit deficiency. This flux is attributable to the high cytosol alpha-glycerophosphate dehydrogenase activity in skeletal muscle. for these reasons the ATP produc...Continue Reading

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