Hafner E W, Wellner D
Biochemistry. 1979 Feb 6;18(3):411-7. doi: 10.1021/bi00570a004.
The reactivity of the imino acids formed in the D- or L-amino acid oxidase reaction was studied. It was found that: (1) When imino acids reacted with the alpha-amino group of glycine or other amino acids, transimination yielded derivatives less stable to hydrolysis than the parent imino acids. In contrast, when imino acids reacted with the epsilon-amino group of lysine or other primary amines, transimination yielded derivatives more stable to hydrolysis than the parent imino acids. (2) Imino acids react rapidly with hydrazine and semicarbazide, forming stable hydrazones and semicarbazones. At pH 7.7, the rate of reaction of the imino acid analogue of leucine with semicarbazide was 10(4) times greater than that of the corresponding keto acid. The reaction of imino acids with these reagents is rapid enough to permit one to follow spectrophotometrically the amino acid oxidase reaction. Imino acids also reacted with cyanide to yield stable adducts. (3) The rate of hydrolysis of the imino acid analogue of leucine was independent of pH above pH 8.5. At lower pH values, the rate of hydrolysis increased with decreasing pH. At 25 degrees C and in the absence of added amino compounds, this imino acid had a half-life of 22 s at pH 8.5. Its half-life was 9.9 s at pH 7.9.
对在D-或L-氨基酸氧化酶反应中形成的亚氨基酸的反应活性进行了研究。结果发现：(1)当亚氨基酸与甘氨酸或其他氨基酸的α-氨基反应时，转亚氨基作用产生的衍生物对水解的稳定性低于母体亚氨基酸。相反，当亚氨基酸与赖氨酸或其他伯胺的ε-氨基反应时，转亚氨基作用产生的衍生物对水解的稳定性高于母体亚氨基酸。(2)亚氨基酸与肼和氨基脲迅速反应，形成稳定的腙和氨基脲。在pH 7.7时，亮氨酸的亚氨基酸类似物与氨基脲的反应速率比相应的酮酸快10⁴倍。亚氨基酸与这些试剂的反应速度足够快，使得可以通过分光光度法跟踪氨基酸氧化酶反应。亚氨基酸也与氰化物反应生成稳定的加合物。(3)亮氨酸的亚氨基酸类似物的水解速率在pH 8.5以上与pH无关。在较低的pH值下，水解速率随pH值的降低而增加。在25℃且不添加氨基化合物的情况下，该亚氨基酸在pH 8.5时的半衰期为22秒。在pH 7.9时其半衰期为9.9秒。
