Esaki N, Seraneeprakarn V, Tanaka H, Soda K
Institute for Chemical Research, Kyoto University, Japan.
J Bacteriol. 1988 Feb;170(2):751-6. doi: 10.1128/jb.170.2.751-756.1988.
We have found a novel enzyme that decomposes D-selenocystine into pyruvate, ammonia, and elemental selenium in extracts of Clostridium sticklandii and C. sporogenes. The enzyme of C. sticklandii has been purified to homogeneity. It has a molecular weight of 74,000 and consists of two subunits identical in molecular weight (35,000). Pyridoxal 5'-phosphate is required as a cofactor. In addition to D-selenocystine, D-cystine, D-lanthionine, meso-lanthionine, and D-cysteine serve as substrates. However, D-selenocysteine, D-serine, DL-selenohomocystine, and L-amino acids are inert. The enzyme also catalyzes the beta-replacement reaction between D-selenocystine and a thiol to produce S-substituted D-cysteine. L-Selenohomocysteine also can serve as a substituent donor in the beta-replacement reaction to yield selenocystathionine.
我们在斯氏梭菌和生孢梭菌提取物中发现了一种新型酶，它可将D-硒代胱氨酸分解为丙酮酸、氨和元素硒。斯氏梭菌的这种酶已被纯化至同质。它的分子量为74,000，由两个分子量相同（35,000）的亚基组成。需要磷酸吡哆醛作为辅因子。除了D-硒代胱氨酸外，D-胱氨酸、D-羊毛硫氨酸、内消旋羊毛硫氨酸和D-半胱氨酸也可作为底物。然而，D-硒代半胱氨酸、D-丝氨酸、DL-硒代高胱氨酸和L-氨基酸是惰性的。该酶还催化D-硒代胱氨酸与硫醇之间的β-取代反应，生成S-取代的D-半胱氨酸。L-硒代高胱氨酸也可作为β-取代反应中的取代基供体，生成硒代胱硫醚。
