Ray P H, Benedict C D, Grasmuk H
J Bacteriol. 1981 Mar;145(3):1273-80. doi: 10.1128/jb.145.3.1273-1280.1981.
Cytidine 5'-triphosphate:cytidine 5'-monophosphate-3-deoxy-D-manno-octulosonate cytidylyltransferase (CMP-KDO synthetase) was purified 2,300-fold from frozen Escherichia coli B cells. The enzyme catalyzed the formation of CMP-KDO, a very labile product, from CTP and KDO. No other sugar tested could replace KDO as an alternate substrate. Uridine 5'-triphosphate at pH 9.5 and deoxycytidine 5'-triphosphate at pH 8.0 and 9.5 could be used as alternate substrates in place of CTP. CMP-KDO synthetase required Mg2+ at a concentration of 10.0 mM for optimal activity. The pH optimum was determined to be between 9.6 and 9.3 in tris(hydroxymethyl)aminomethane-acetate or sodium-glycine buffer. This enzyme had an isoelectric point between pH 4.15 and 4.4 and appeared to be a single polypeptide chain with a molecular weight of 36,000 to 40,000. The apparent Km values for CTP and KDO in the presence of 10.0 mM Mg2+ were determined to be 2.0 X 10(-4) and 2.9 X 10(-4) M, respectively, at pH 9.5. Uridine 5'-triphosphate and deoxycytidine 5'-triphosphate had apparent Km values of 8.8 X 10(-4) and 3.4 X 10(-4) M. respectively, at pH 9.5.
胞苷5'-三磷酸：胞苷5'-单磷酸-3-脱氧-D-甘露糖辛酮酸胞苷酰转移酶（CMP-KDO合成酶）从冷冻的大肠杆菌B细胞中纯化了2300倍。该酶催化由CTP和KDO形成CMP-KDO，一种非常不稳定的产物。测试的其他糖类均不能替代KDO作为替代底物。在pH 9.5时的尿苷5'-三磷酸以及在pH 8.0和9.5时的脱氧胞苷5'-三磷酸可替代CTP用作替代底物。CMP-KDO合成酶需要浓度为10.0 mM的Mg2+以实现最佳活性。在三（羟甲基）氨基甲烷-乙酸盐或甘氨酸钠缓冲液中，最适pH值确定为9.6至9.3之间。该酶的等电点在pH 4.15至4.4之间，似乎是一条分子量为36,000至40,000的单多肽链。在pH 9.5、存在10.0 mM Mg2+的情况下，CTP和KDO的表观Km值分别确定为2.0×10^(-4)和2.9×10^(-4) M。在pH 9.5时，尿苷5'-三磷酸和脱氧胞苷5'-三磷酸的表观Km值分别为8.8×10^(-4)和3.4×10^(-4) M。
