Alanine racemase of alfalfa seedlings (Medicago sativa L.):: First evidence for the presence of an amino acid racemase in plants
Alanine racemase of alfalfa seedlings (Medicago sativa L.):: First evidence for the presence of an amino acid racemase in plants
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DOI：
10.1016/j.phytochem.2006.02.017
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发表时间：
2006-05-01
期刊：
影响因子：
3.8
通讯作者：
Soda, Kenji
中科院分区：
文献类型：
--
作者：
Ono, Kazutoshi;Yanagida, Kazuki;Soda, Kenji
我们在植物幼苗中发现了几种d -氨基酸，并在苜蓿幼苗中发现了丙氨酸消旋酶（E.C.5.1.1.1）。这是植物中氨基酸消旋酶存在的第一个证据。添加L-丙氨酸或d -丙氨酸可有效诱导该酶，并对该酶进行了高纯度纯化，以显示其酶学特性。这种酶专门催化L-丙氨酸和d -丙氨酸的外消旋。l -丙氨酸酶的K-m和V-max分别为29.6 × 10(-3) M和1.02 mol/s/kg， d -丙氨酸酶的K-m和V-max分别为12.0 × 10(-3) M和0.44 mol/s/kg。K-eq值估计约为1，表明该酶可催化丙氨酸两种对映体的典型外消旋作用。羟胺、苯肼和其他吡哆醛5′-磷酸酶抑制剂使该酶失活。因此，该酶需要吡哆醛5'-磷酸作为辅酶，酶学上类似于目前研究的细菌丙氨酸消旋酶。(c) 2006 Elsevier Ltd.版权所有。
We demonstrated several kinds Of D-amino acids in plant seedlings, and moreover alanine racemase (E.C.5.1.1.1) in alfalfa (Medicago sativa L.) seedlings. This is the first evidence for the presence of amino acid racemase in plant. The enzyme was effectively induced by the addition Of L- or D-alanine, and we highly purified the enzyme to show enzymological properties. The enzyme exclusively catalyzed racemization Of L- and D-alanine. The K-m and V-max values of enzyme for L-alanine were 29.6 x 10(-3) M and 1.02 mol/s/kg, and those for D-alanine are 12.0 x 10(-3) M and 0.44 mol/s/kg, respectively. The K-eq value was estimated to be about I and indicated that the enzyme catalyzes a typical racemization of both enantiomers of alanine. The enzyme was inactivated by hydroxylamine, phenylhydrazine and some other pyridoxal 5'-phosphate enzyme inhibitors. Accordingly, the enzyme required pyridoxal 5'-phosphate as a coenzyme, and enzymologically resembled bacterial alanine racemases studied so far. (c) 2006 Elsevier Ltd. All rights reserved.