豇豆固氮根瘤中尿酸氧化酶的纯化及某些性质

Purification and some properties of urate oxidase from nitrogen-fixing nodules of cowpea.

作者信息

Rainbird R M, Atkins C A

出版信息

Biochim Biophys Acta. 1981 May 14;659(1):132-40. doi: 10.1016/0005-2744(81)90277-1.

Abstract

Urate oxidase (urate: oxygen oxidoreductase, EC 1.7.3.3) was purified 166-fold from nitrogen-fixing root nodules of cowpea Vigna unguiculata [L.] Walp. The purified enzyme showed a specific activity of 5.7 mumol urate oxidised/min per mg protein, a molecular mass of 100 kdaltons, pH optimum between 9 and 10, isoelectric point at PH 6.8, Km(urate) = 18 muM and Km(oxygen) = 29 muM. A number of metal complexing and chelating reagents were inhibitory, as were divalent cations, including Cu2+. Iron stimulated the enzyme. Low concentrations of ammonia, glutamine and xanthine were also inhibitory. The regulation of urate oxidase in relation to the assimilation of fixed nitrogen in legume nodules is discussed.

摘要

从豇豆（Vigna unguiculata [L.] Walp.）的固氮根瘤中纯化出了尿酸氧化酶（尿酸：氧氧化还原酶，EC 1.7.3.3），纯化倍数为166倍。纯化后的酶比活性为每毫克蛋白质每分钟氧化5.7微摩尔尿酸，分子量为100千道尔顿，最适pH值在9至10之间，等电点为pH 6.8，尿酸的米氏常数（Km(urate)）= 18微摩尔，氧的米氏常数（Km(oxygen)）= 29微摩尔。许多金属络合剂和螯合剂具有抑制作用，二价阳离子包括Cu2+也是如此。铁能刺激该酶。低浓度的氨、谷氨酰胺和黄嘌呤也有抑制作用。本文讨论了尿酸氧化酶与豆科植物根瘤中固定氮同化的关系。