Über l(—)-Phenylalaninoxydase

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Abstract
Specific enzymes are known for the catabolism of about half the l-amino acids. Most d-amino acids undergo oxidative deamination by the same d-amino acid oxidase. To determine whether a 1([long dash])-phenylalaninoxidase exists, dogs and rats were killed by decapitation, their livers and kidneys ground with sand and extracted at 0[degree] with M/10 or M/5 phosphate buffer, pH 8. The mixture was cen-trifugalized and the clear enzyme soln. obtained. The activity of the oxidase soln. was detd. by manometric measurement of the O2 consumption in the Warburg apparatus. The reaction mixture contained 2.1 ml. enzyme soln. (corresponding to 1.6-1.8 g. fresh liver), 0.1 ml. 2 [image] KOH, and 1 ml. [image]/100 1([long dash])-phenylalanine in [image]/2 phosphate soln. pH 8. The enzyme extract attacked 1([long dash])-phenylalanine with the uptake of 1 atom of O and without splitting off NH. It also oxidized 1([long dash])-tyrosine without splitting off NH3, so that both amino acids were probably acted on by the same enzyme. The 1([long dash])-phenylalaninoxi-dase was present in liver but not in kidney. The conc. of the oxidase was greater in the liver of the rat than in that of the dog. The oxidase was probably not a yellow enzyme. Dialysis of the extract against [image]/100 phosphate buffer, pH 8, removed some factor essential for the activity of the enzyme system. HCN, Cu, Mn, Zn and Mg did not inhibit the enzyme, while 10-4 [image] CoCl2 decreased its activity. Attempts to concentrate and purify the enzyme were not successful because of its instability.

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