Glyceraldehyde and Embryonic Glucolysis

Abstract

IT has already been reported1,2 that anaerobic lactic acid production from glucose in the chick embryo is a true case of non-phosphorylating glucolysis, strongly inhibited by dl-glyceraldehyde. As possible intermediates, glycerol, glyceric acid, dihydroxyacetone and methylglyoxal were excluded. We are now able to add to the list pyruvic acid and glyceraldehyde.* Of the two stereoisomers, only l-glyceraldehyde inhibits glucolysis ; this corresponds in its configuration to l-lactic acid (sarcolactic acid) which derives from glucose in the body. The inhibitory effect is complete at a concentration of about 2·5 × 10-3 M. The fact that dl-glyceraldehyde does not apparently inhibit glucolysis more than about 90 per cent is due to a slow enzymic lactic acid formation from glyceraldehyde itself. This process needs glutathione as co-enzyme and is not based upon a primary condensation of trioses to hexose, as it is not inhibited by amounts of fluoride or iodoacetate which would be enough to poison a secondary glucose breakdown. It is due rather to the non-enzymic formation of methylglyoxal under the experimental conditions, which is then converted to lactic acid by the glyoxalase present.