Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CSIC), E-28049 Madrid, Spain.
J Exp Bot. 2011 Jan;62(1):307-18. doi: 10.1093/jxb/erq268. Epub 2010 Sep 2.
Ureidoglycolate is an intermediate in the degradation of the ureides, allantoin and allantoate, found in many organisms. In some leguminous plant species these compounds are used to transport recently fixed nitrogen in the root nodules to the aerial parts of the plant. In the present study, it was demonstrated that purified ureidoglycolases from chickpea (Cicer arietinum) and French bean (Phaseolus vulgaris) do not produce glyoxylate, and can use phenylhydrazine as a substrate with K(m) values of 4.0 mM and 8.5 mM, respectively. Furthermore, these enzymes catalyse the transfer of the ureidoglycolyl group to phenylhydrazine to produce ureidoglycolyl phenylhydrazide, which degrades non-enzymatically to glyoxylate phenylhydrazone and urea. This supports their former classification as ureidoglycolate urea-lyases. The enzymatic reaction catalysed by the characterized ureidoglycolases uncovered here can be viewed as a novel type of phenylhydrazine ureidoglycolyl transferase. The implications of these findings for ureide metabolism in legume nitrogen metabolism are discussed.
脲基乙醇酸是许多生物体中尿囊素和尿囊酸盐降解的中间产物。在一些豆科植物物种中，这些化合物被用于将根瘤中最近固定的氮运输到植物的地上部分。在本研究中，已证明鹰嘴豆（Cicer arietinum）和菜豆（Phaseolus vulgaris）的纯化脲基乙醇酸酶不产生乙醛酸，并且可以使用苯肼作为底物，其 K(m) 值分别为 4.0 mM 和 8.5 mM。此外，这些酶催化将脲基乙醇酰基转移到苯肼上，生成脲基乙醇酰基苯肼，该化合物非酶促降解为乙醛酸苯腙和尿素。这支持了它们以前作为脲基乙醇酸脲酶的分类。在这里表征的脲基乙醇酸酶催化的酶反应可以看作是一种新型的苯肼脲基乙醇酰基转移酶。讨论了这些发现对豆科植物氮代谢中尿嘧啶代谢的意义。
