The decrease in reducing power of ovomucoid during proteolysis

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Abstract
When incubated with proteolytic enzymes the reducing power of ovomucoid falls, in some cases to as little as 30% of its original value. The reducing power of chymotrypsinogen falls in a similar way, showing that this loss of reducing power is not necessarily associated with the carbohydrate moiety. When reducing sugars were added to digests of ovomucoid, the total reducing power of these mixtures was less than the sum of the individual reducing powers of sugar and digest when measured separately. This discrepancy increased during the course of digestion. Several amino acids, particularly cysteine, cystine, serine and tryptophan, show reducing power towards Somogyi''s reagent. Possible mechanisms for the reduction of copper by cysteine, serine and other amino acids, and for the decrease in reducing power on proteolysis, are discussed. The bearing of these results on the suggested O-glycosidic link between carbohydrate and protein in ovomucoid (Hartley and Jevons, 1962) is considered. The main experimental basis for this hypothesis is removed.

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