Serafini-Cessi F, Dall'Olio F
Biochem J. 1983 Dec 1;215(3):483-9. doi: 10.1042/bj2150483.
A beta-N-acetylgalactosaminyltransferase that preferentially transferred N-acetylgalactosamine to Sd(a-) Tamm-Horsfall glycoprotein was found in guinea-pig kidney microsomal preparations. This enzyme was kidney-specific and was able to transfer the sugar to other glycoproteins, such as fetuin and alpha 1-acidic glycoprotein. The presence of sialic acid in the acceptors was essential for the transferase activity when either glycoproteins or their Pronase glycopeptides were used as acceptors. Two glycopeptides (Tamm-Horsfall glycopeptides I and II) with a different carbohydrate composition were separated by DEAE-Sephacel chromatography from Pronase-digested Tamm-Horsfall glycoprotein. The amount of N-acetylgalactosamine transferred to glycopeptides by the enzyme correlated with their degree of sialylation. Enzymic digestion of N-[14C]acetylgalactosamine-labelled Tamm-Horsfall glycopeptide II showed that the transferred sugar was susceptible to beta-N-hexosaminidase. The amount of sugar cleaved by beta-hexosaminidase was strongly increased when the labelled Tamm-Horsfall glycopeptide II was pretreated with mild acid hydrolysis, a procedure that removed the sialic acid residues. Alkaline borohydride treatment of the labelled Tamm-Horsfall glycopeptide II did not release radioactivity, thus indicating that enzymic glycosylation took place at the N-asparagine-linked oligosaccharide units of Tamm-Horsfall glycoprotein.
在豚鼠肾微粒体制剂中发现了一种β-N-乙酰半乳糖胺基转移酶，它优先将N-乙酰半乳糖胺转移至Sd(a-)Tamm-Horsfall糖蛋白。该酶具有肾脏特异性，并且能够将该糖转移至其他糖蛋白，如胎球蛋白和α1-酸性糖蛋白。当使用糖蛋白或其链霉蛋白酶糖肽作为受体时，受体中唾液酸的存在对于转移酶活性至关重要。通过DEAE-葡聚糖凝胶色谱法从链霉蛋白酶消化的Tamm-Horsfall糖蛋白中分离出两种碳水化合物组成不同的糖肽（Tamm-Horsfall糖肽I和II）。该酶转移至糖肽的N-乙酰半乳糖胺的量与其唾液酸化程度相关。对N-[14C]乙酰半乳糖胺标记的Tamm-Horsfall糖肽II进行酶消化表明，转移的糖对β-N-己糖胺酶敏感。当标记的Tamm-Horsfall糖肽II用温和酸水解预处理（该程序去除了唾液酸残基）时，β-己糖胺酶切割的糖量大幅增加。对标记的Tamm-Horsfall糖肽II进行碱性硼氢化物处理未释放出放射性，因此表明酶促糖基化发生在Tamm-Horsfall糖蛋白的N-天冬酰胺连接的寡糖单元上。
