Studies on Animal Diastases

Within comparatively recent years, many studies have been carried out on blood diastase, with the object in view, first, of elucidating the source, or sources, of this enzyme in the circulating blood, and, secondly, of determining the part, if any, which it plays in carbohydrate metabolism. From a review of the literature, it is evident that the findings of different investigators have in many instances failed to agree. It was thought that this lack of uniformity in the results obtained might be due to differences in the methods used to estimate quantitatively the amount of diastase in the blood, and that a comparison of the most commonly employed methods might throw some light on this subject. Hitherto, the quantitative estimation of diastase in blood has been effected by one of four different methods: (1) the method of Wohlgemuth (l), which depends on the rate of disappearance of soluble starch, as shown by the starch-iodine color test; (2) the achromic point method of Roberts (2), which is also dependent upon the reaction of the products to iodine; (3) sugar reduction methods, by which the enzyme is quantitatively estimated according to the amount of reducing sugars formed from the hydrolysis of starch or glycogen; (4) the viscosimetric method of Elman and McCaughan (3). This method depends on the time required to effect a 20 per cent reduction in the viscosity of a solution of soluble starch. Evans (4) in a criticism of the Wohlgemuth and achromic point methods, concludes that, for quantitative comparisons, neither method is satisfactory, and that the best results are obtained with a