Abstract
It has been suggested by Lipmann 1 that the enzyme (or one component of the enzyme system) of muscle extract which is capable of converting glycogen into lactic acid is reversibly oxidizable and reducible and is active as an enzyme only in its reduced state. This hypothesis was seemingly confirmed by Michaelis and Runnström. 2 The evidence presented by the latter authors for the reactivation of a muscle extract which had become partially or completely inactive by standing exposed to the air was as follows. If such an extract was treated with a neutralized solution of thioglycollic acid and then subjected to a manometric experiment, with the addition of sodium bicarbonate and a suitable partial pressure of CO2, a definite and sustained positive pressure was recorded on the manometer. If the thioglycollate was replaced by water a much smaller pressure or no pressure was recorded. This evidence was strengthened by the finding of a small but definite increase in lactic acid in the thioglycollate experiment as compared with the control.
Certain difficulties in preparing the mixtures containing thioglycollate for the application of the Friedemann, Cotonio and Shaffer 3 method for lactic acid were mentioned in the earlier paper, but it was believed that they had been overcome. We have now to report that this increase in lactic acid cannot be confirmed.
The method used by us is as follows: The contents of a respiration vessel amounting to about 2.5 cc.∗ is diluted to 20.0 cc. with H2O, 10.0 cc. of a 20% CuSO4 solution is added gradually with constant shaking, and 10.0 cc. of a 10% suspension of calcium hydroxide is then added. After thorough mixing the solution should be definitely alkaline to litmus.
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