Weidanz J A, Campbell P, DeLucas L J, Jin J, Moore D, Rodén L, Yu H, Heilmann E, Vezza A C
Department of Microbiology, School of Medicine, University of Alabama at Birmingham 35294-2170, USA.
Br J Haematol. 1995 Sep;91(1):72-9. doi: 10.1111/j.1365-2141.1995.tb05247.x.
In the course of an investigation of hexosamine catabolism in the human malaria parasite, Plasmodium falciparum, it became apparent that a basic understanding of the relevant enzymatic reactions in the host erythrocyte is lacking. To acquire the necessary basic knowledge, we have determined the activities of several enzymes involved in hexosamine metabolism in normal human red blood cells. In the present communication we report the results of studies of glucosamine 6-phosphate deaminase (GlcN6-P) using a newly developed sensitive radiometric assay. The mean specific activity in extracts of fresh erythrocytes assayed within 4h of collection was 14.7 nmol/h/mg protein, whereas preparations from older erythrocytes that had been stored at 4 degrees C for up to 4 weeks had a mean specific activity of 6.2 nmol/h/mg. Characterization of the deaminase by chromatofocusing gave a pI of 8.55. The enzyme was optimally active at pH 9.0 and had a Km of 41 microM. The metal chelators EDTA and EGTA were non-inhibitory; however, inhibition was observed in the presence of metal ions, especially Cu2+, Ni2+ and Zn2+. In addition, the deaminase was also inhibited by several sugar phosphates including the reaction product, fructose 6-phosphate.
在对人类疟原虫恶性疟原虫中己糖胺分解代谢的研究过程中，很明显缺乏对宿主红细胞中相关酶促反应的基本了解。为了获得必要的基础知识，我们测定了正常人类红细胞中参与己糖胺代谢的几种酶的活性。在本报告中，我们使用新开发的灵敏放射性测定法报告了对6-磷酸葡糖胺脱氨酶（GlcN6-P）的研究结果。采集后4小时内测定的新鲜红细胞提取物中的平均比活性为14.7 nmol/h/mg蛋白质，而在4℃下储存长达4周的较老红细胞的制剂的平均比活性为6.2 nmol/h/mg。通过色谱聚焦对脱氨酶进行表征，其pI为8.55。该酶在pH 9.0时活性最佳，Km为41μM。金属螯合剂EDTA和EGTA无抑制作用；然而，在金属离子尤其是Cu2+、Ni2+和Zn2+存在下观察到抑制作用。此外，该脱氨酶还受到几种糖磷酸酯的抑制，包括反应产物6-磷酸果糖。
