Glycolysis by Human Spermatozoa: Levels of Glycolytic Intermediates

Abstract

The steady-state levels of glycolytic intermediates of washed sperm suspensions containing glucose under aerobic and anaerobic conditions were determined from perchloric acid extracts. Under both conditions, the products of the phosphofructokinase and aldolase steps accumulate and substantially exceed the level of hexose monophosphates. These high levels of triose phosphate and fructose diphosphate do not appear to be the result of an unfavorable NAD⁺/NADH equilibrium since added pyruvate does not substantially reduce their accumulation in washed cells and since the same intermediates accumulate in semen where pyruvate concentrations are normally high. The aerobic metabolite levels apparently reflect the inability of oxidative metabolism in human sperm to develop high levels of ATP and also suggest possible sites of glycolytic control at either glyceraldehyde phosphate dehydrogenase or phosphoglycerate kinase. Concentrations of α-glycerophosphate in sperm were found to be low; the reasons for this and its possible significance for glycolysis are discussed.