On the mechanism of the inhibition of glycolysis by glyceraldehyde

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Abstract
It is suggested that inhibition of triosephosphate dehydrogenase may play an important part in the well known inhibition of glycolysis by glyceraldehyde. In a system consisting of muscle extract reinforced with yeast hexokinase, the inhibition can be delayed by addition of pure triosephosphate dehydrogenase. Other indirect evidence indicating the part played by inhibition of glyceraldehydephosphate oxidation in this system is also given. The reduction of coenzyme I by glyceraldehydephosphate in presence of pure triosephosphate dehydrogenase is inhibited by DL-glyceraldehyde. This happens with the enzyme in absence of cysteine and also after cysteine activation. In the absence of cysteine, the degree of inhibition was found to depend upon the concn. of glyceraldehydephosphate. The inhibition of the cysteine-activated enzyme could be largely overcome by addition of more cysteine. When D-glyceraldehyde was compared with DL-glyceraldehyde, it appeared that the inhibition of pure enzyme was entirely due to the D-form. With the system consisting of muscle extract with yeast hexokinase, D-glyceraldehyde caused inhibition of glycolysis, but the effect was not as great as that of twice the amount of DL-glyceraldehyde. In the latter system there was some evidence that glycerophosphate dehydrogenase was also inhibited by D-glyceraldehyde. The inhibition of the hexokinase of rat-muscle extract by DL-glyceraldehyde was confirmed. It was found that the degree of inhibition depends on the concn. of glucose present; in the presence of 0.002 [image] glyceraldehyde the enzyme was entirely protected by 0.004 [image] glucose. About 3 times this concn. of fructose is necessary to protect the hexokinase.
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