谷氨酸棒杆菌中的尿素摄取与脲酶活性

Urea uptake and urease activity in Corynebacterium glutamicum.

作者信息

Siewe R M, Weil B, Burkovski A, Eggeling L, Krämer R, Jahns T

机构信息

Institut für Biotechnologie 1, Forschungszentrum Jülich GmbH, Jülich, Germany.

出版信息

Arch Microbiol. 1998 May;169(5):411-6. doi: 10.1007/s002030050591.

DOI:10.1007/s002030050591

PMID:9560422

Abstract

When Corynebacterium glutamicum is grown with a sufficient nitrogen supply, urea crosses the cytoplasmic membrane by passive diffusion. A permeability coefficient for urea diffusion of 9 x 10(-7) cm s-1 was determined. Under conditions of nitrogen starvation, an energy-dependent urea uptake system was synthesized. Carrier-mediated urea transport was catalyzed by a secondary transport system linked with proton motive force. With a Km for urea of 9 microM, the affinity of this uptake system was much higher than the affinity of urease towards its substrate (Km approximately 55 mM urea). The maximum uptake velocity depended on the expression level and was relatively low [2-3.5 nmol min-1 (mg dry wt.)-1].

摘要

当谷氨酸棒杆菌在有充足氮供应的条件下生长时，尿素通过被动扩散穿过细胞质膜。测定了尿素扩散的渗透系数为9×10⁻⁷ cm s⁻¹。在氮饥饿条件下，合成了一种能量依赖型尿素摄取系统。载体介导的尿素转运由与质子动力相关的次级转运系统催化。该摄取系统对尿素的Km值为9 μM，其对尿素的亲和力远高于脲酶对其底物的亲和力（Km约为55 mM尿素）。最大摄取速度取决于表达水平，且相对较低[2 - 3.5 nmol min⁻¹ (mg干重)⁻¹]。