Studies on the enzymatic production of nucleosides in the activated methyl cycle

研究了一种以粪芽孢杆菌细胞为催化剂，以l -同型半胱氨酸及相应核苷为原料，制备AdoHcy及相关核苷的简单高效方法。然而，参与一种酶的活性，可以催化D-和l -同型半胱氨酸异构体在与粪芽孢杆菌细胞的反应体系中的相互转化，似乎很有希望解决这个问题。基于这个想法，我们再次筛选了能够同时利用D-和l -同型半胱氨酸异构体作为底物的微生物。结果发现，恶臭假单胞菌IFO 12996和其他几种细菌菌株可作为腺苷和d -同型半胱氨酸转化为l型adhcy的催化剂。但在实际应用中，粪芽孢杆菌细胞仍优于恶臭假单胞菌细胞，因为粪芽孢杆菌细胞具有较高的adhcy水解酶活性和较低的腺苷脱氨酶活性。因此，我们只使用p.p putida细胞作为消旋酶的来源。通过将腺苷和D， l -同型半胱氨酸与粪芽孢杆菌细胞和恶臭芽孢杆菌细胞混合在磷酸钾黄油中，我们基本上获得了100%的产率。以类似的方式，一些新的s -核苷同型半胱氨酸可以有效地从相应的腺苷类似物和l -同型半胱氨酸合成。k -卡拉胶包埋的粪单胞在重复反应中表现出较高的稳定性，而游离细胞的失活速度较快。这些新型的s -核苷型同型半胱氨酸在药物和化疗领域也具有广阔的应用前景。

We have developed a simple and efficient method for the production of AdoHcy and related nucleosides from L-homocysteine and corresponding nucleosides with A. faecalis cells as catalysts.However, the involvement of an enzyme activity that can catalyze the interconversion of the D- and L-homocysteine isomers in the reaction system with A. faecalis cells seems very promising as a means of solving this problem. Based on this idea, we again screened microorganisms capable of utilizing both the D- and L-homocysteine isomers as substrater. As a result of this screening, Pseudomonas putida IFO 12996 and several other bacterial strains were found to act as catalysts for the conversion of adenosine and D-homocysteine to the L-form of Adohcy. For practical purposes,though, A. faecalis cells were still superior to P. putida cells because they showed high AdoHcy hydrolase activity and low adenosine deaminase activity. Therefore, we used P. putida cells only as a source of the racemase. By mixing adenosine and D,L-homocysteine with a mixture of A. faecalis cells and P. putida cells in potassium phosphate butter, we essentially obtained a 100% yield.In a similar manner, several novel S-nucleosidylhomocysteines could be synthesized efficiently from the corresponding adenosine analogues and L-homocysteine. The K-carrageean entrapped cells of A. faecalis showed high stability on repeated reactions, whereas free cells were inactivated rapidly. These novel S-nucleosidylhomocysteines alsocould be promising for application in the pharmaceutical and chemotherapeutic fields.