van Dijk W, Lasthuis A M, van den Eijnden D H
Biochim Biophys Acta. 1979 Apr 18;584(1):129-42. doi: 10.1016/0304-4165(79)90243-5.
CMP-AcNeu:glycoprotein sialyltransltransltransltransltransferase of calf kidney cortex was characterized using serum glycoproteins and Tamm-Horsfall glycoprotein, obtained from calf urine, as acceptors. Native calf Tamm-Horsfall glycoprotein showed the best acceptor properties, followed by desialylated calf fetuin and desialylated human alpha 1-acid glycoprotein exhibiting V values of, respectively, 114, 63 and 41 nmol/h per g wet wt. of kidney cortex and Km values of 0.12, 0.16 and 0.26 mM glycoprotein acceptor. Desialylated ovine submaxillary mucine appeared to be a very poor acceptor. Tamm-Horsfall glycoprotein sialyltransferase could be distinguished from serum glycoprotein sialyltransferase by competition studies. In addition the two glycoprotein sialyltransferase activities showed different distributions over the three regions of the calf kidney: the ratios of the Tamm-Horsfall to serum glycoprotein sialyltransferase activities decreased from 3.3 in the cortex to 0.8 and 0.4 in the medulla and the papilla, respectively. It was concluded that in calf kidney at least two different sialyltransferases exist. The high cortical Tamm-Horsfall glycoprotein sialyltransferases activity corresponds markedly to the origin of the urinary Tamm-Horsfall glycoprotein, namely the distal part of the kidney tubule. Inactivation of glycoprotein sialyltransferase activity by preincubation at various temperatures and during storage at 0 degree C, could be reduced by the addition of CMP-AcNeu. The possible relevance towards the in vivo sialylation of this finding is discussed.
CMP - N - 乙酰神经氨酸：以血清糖蛋白和从小牛尿液中获得的Tamm - Horsfall糖蛋白作为受体，对小牛肾皮质的糖蛋白唾液酸转移酶进行了特性研究。天然小牛Tamm - Horsfall糖蛋白表现出最佳的受体特性，其次是去唾液酸化的小牛胎球蛋白和去唾液酸化的人α1 - 酸性糖蛋白，其V值分别为每克肾皮质湿重114、63和41 nmol/h，糖蛋白受体的Km值分别为0.12、0.16和0.26 mM。去唾液酸化的绵羊下颌粘蛋白似乎是一种非常差的受体。通过竞争研究可以将Tamm - Horsfall糖蛋白唾液酸转移酶与血清糖蛋白唾液酸转移酶区分开来。此外，两种糖蛋白唾液酸转移酶活性在小牛肾的三个区域表现出不同的分布：Tamm - Horsfall糖蛋白与血清糖蛋白唾液酸转移酶活性的比值从皮质中的3.3分别降至髓质和乳头中的0.8和0.4。得出的结论是，在小牛肾中至少存在两种不同的唾液酸转移酶。皮质中高活性的Tamm - Horsfall糖蛋白唾液酸转移酶与尿中Tamm - Horsfall糖蛋白的来源，即肾小管远端，明显对应。在不同温度下预孵育以及在0℃储存期间，糖蛋白唾液酸转移酶活性的失活可通过添加CMP - N - 乙酰神经氨酸来降低。讨论了这一发现与体内唾液酸化的可能相关性。
