Apparent differences in pH optima among isozymes of glycerol-3-phosphate dehydrogenase, hexokinase, and lactate dehydrogenase in the earthworm Eisenia fetida

Abstract

1. Isozymes of glycerol-3-phosphate dehydrogenase (GPD-1, GPD-2), hexokinase (HK-1, HK-2), and lactate dehydrogenase (LDH-1, LDH-2) were assayed between pH 6.0 and 11.0 in the earthworm Eisenia fetida. 2. Isozymes encoded by loci producing a heterozygosity-growth relationship (GPD-2, HK-2, LDH-1) were most active near pH 9.5; other isozymes were most active near pH 7.5. 3. Tissue pH ranged from 6.65 to 7.46 and varied with soil pH and soil moisture but not exercise. 4. Environmentally-induced changes in tissue pH were probably not sufficient to influence isozymal activity and may not affect whether loci participate in the heterozygosity-growth phenomenon. © 1991.