Richards N G, Schuster S M
Department of Chemistry, University of Florida, Gainesville 32611.
FEBS Lett. 1992 Nov 23;313(2):98-102. doi: 10.1016/0014-5793(92)81421-h.
In the absence of crystallographic data, the mechanism of nitrogen transfer from glutamine in asparagine synthetase (AS) remains under active investigation. Surprisingly, the glutamine-dependent AS from Escherichia coli (AsnB) appears to lack a conserved histidine residue, necessary for nitrogen transfer if the reaction proceeds by the accepted pathway in other glutamine amidotransferases, but retains the ability to synthesize asparagine. We propose an alternative mechanism for nitrogen transfer in AsnB which obviates the requirement for participation of histidine in this step. Our hypothesis may also be more generally applicable to other glutamine-dependent amidotransferases.
在缺乏晶体学数据的情况下，天冬酰胺合成酶（AS）中谷氨酰胺的氮转移机制仍在积极研究中。令人惊讶的是，来自大肠杆菌的谷氨酰胺依赖性AS（AsnB）似乎缺少一个保守的组氨酸残基，而如果反应按照其他谷氨酰胺酰胺转移酶中公认的途径进行，该残基是氮转移所必需的，但它仍保留合成天冬酰胺的能力。我们提出了AsnB中氮转移的另一种机制，该机制排除了组氨酸参与这一步骤的必要性。我们的假设可能也更普遍适用于其他谷氨酰胺依赖性酰胺转移酶。
