Weitere Untersuchungen über die Hydrolyse von d-Tripeptiden durch Serumenzyme

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Abstract
The prepn. of d-amino acid oxidase soln. and the methods for carrying out the expts. were descr. previously (Hoppe-Seyler''s Zeitschr. Physiol. Chem., 269: 53, 1941). The reaction mixtures usually contained 0.5 ml. serum, 1 ml. M/10 tripeptide substrate, and 1 ml. 0.15 M phosphate buffer, pH 7.4. The mixtures were incubated 0-120 hrs., and the amt. of d-tripeptide hydrolyzed detd. by deaminating the reaction mixture with 0.5 ml. of the d-amino acid oxidase in the Warburg apparatus at 37.5[degree]. Using d-alanylglycyl-glycine and d-leucylglycylglycine as substrates, the d-tri-peptidase activity of the serum of 21 patients with carcinoma, 17 patients suffering from such diseases as pneumonia, tuberculosis, nephritis, stomach ulcers, etc., and 2 normal subjects was detd. In all cases, more d-alanylglycyl-glycine than d-leucylglycylglycine was hydrolyzed. d-Alanyl-glycylglycine was split 0-11.4% by the carcinomatous serum and 0-6.9% by the non-carcinomatous serum, while the respective values for d-leucylglycylglycine were 0-4.4% and 0-1.2%. An increased hydrolysis of d-alanylglycylglycine was not to be regarded as specific for cancer, but rather as a pathologic change in the enzyme economy of the serum. The peptidase might be increased because of cell destruction in the body, or the activity of the enzymes normally present might be increased. When d-valylglycylglycine was used as substrate, about the same results were obtained as with d-leucylglycylglycine.

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