Brand L M, Harper A E
Biochemistry. 1976 May 4;15(9):1814-21. doi: 10.1021/bi00654a005.
Histidine ammonia-lyase (EC 4.3.1.3) from rat liver was purified more than 250-fold to near homogeneity. Electrophoretic determinations indicated a native molecular weight of approximately 200,000. The enzyme has a pH optimum of approximately pH 8.5. The minimum Km for L-histidine was 0.5 mM at pH 9.0. The Michaelis constant in the physiological pH range was, however, more than 2.0 mM. D-alpha-hydrazinoimidazolylpropionic acid was found to be a potent competitive inhibitor of liver histidine ammonia-lyase (Kis=75 muM); the L enantiomer of this compound was less effective in this regard. The enzyme was also inhibited competitively by L-histidine hydroxamate (Kis=0.4 mM), and to a lesser extent by L-histidinol, D-histidine, and glycine. Failure of a wide variety of other histidine analogues to inhibit the enzyme substantially indicates high specificity of the active site for L-histidine. No alternate substrates were identified for the enzyme. DL-alpha-Hydrazinophenylpropionic acid, the alpha-hydrzino analogue of phenylalanine, was similarly shown to be a very potent competitive inhibitor of a mechanistically similar L-phenylalanine ammonia-lyase purified from Rhodotorula glutinis. The properties of histidine ammonia-lyase from rat liver differ significantly from those of the enzyme from Pseudomonas fluorescens which has been studied most extensively to date.
大鼠肝脏中的组氨酸解氨酶（EC 4.3.1.3）被纯化了250多倍，达到近乎纯的状态。电泳测定表明其天然分子量约为200,000。该酶的最适pH约为8.5。在pH 9.0时，L-组氨酸的最小Km为0.5 mM。然而，在生理pH范围内的米氏常数超过2.0 mM。发现D-α-肼基咪唑基丙酸是肝脏组氨酸解氨酶的有效竞争性抑制剂（Kis = 75 μM）；该化合物的L对映体在这方面效果较差。该酶也被L-组氨酸异羟肟酸竞争性抑制（Kis = 0.4 mM），并在较小程度上被L-组氨醇、D-组氨酸和甘氨酸抑制。多种其他组氨酸类似物未能显著抑制该酶，这表明活性位点对L-组氨酸具有高度特异性。未鉴定出该酶的替代底物。DL-α-肼基苯丙酸，苯丙氨酸的α-肼基类似物，同样被证明是从粘红酵母中纯化的机制相似的L-苯丙氨酸解氨酶的非常有效的竞争性抑制剂。大鼠肝脏组氨酸解氨酶的性质与迄今为止研究最广泛的荧光假单胞菌中的该酶的性质有显著差异。
