Guinea-pig kidney β-N-acetylgalactosaminyltransferase towards Tamm-Horsfall glycoprotein. Requirement of sialic acid in the acceptor for transferase activity

Abstract

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.

The Asn‐linked carbohydrate chains of human Tamm‐Horsfall glycoprotein of one male

“…As in previous reports on Cad-active mucins (Blanchard et al, 1983;Herkt et al, 1985;Nasir-Ud-Din et al, 1986) and Sd"-active T-H glycoprotein (Donald et al, 1983;Donald and Feeney, 1986;Williams et al, 1984), no terminal GalNAcfll-4GalPl-or NeuSAca2-6(GalNAc/Il~ 4)Gal/II-element was found. This is in agreement with biosynthetic studies with fi-N-acetylgalactosaminyltransferases from guinea-pig kidney (Serafini-Cessi and Dall'Olio, 1983), human kidney (Piller et al, 1986), human blood plasma (Takeya et al, 1987) and human urine (Serafini-Cessi et al, 1988), which have demonstrated that the transferases require a2 -3-linked sialic acid in the acceptor.…”

Comparative study of glycophorin A derived O-glycans from human Cad, Sd(a+) and Sd(a-) erythrocytes

“…It is therefore expected that the (fl -4)GalNAc transferases involved in biosynthesis of Cad and Sda antigens might also be different. (,/1-4)GalNAc transferases were recently reported in guinea-pig kidney (Serafini-Cessi & Dall'Olio, 1983) and in a murine cytotoxic T-cell line (Conzelmann & Kornfeld, 1984) and both enzymes were able to transfer [14C]GalNAc from UDP-[14C]GalNAc to human glycophorin as expected for the blood group Cad enzyme. However, experiments from our group suggest that the (/1l-4)GalNAc from human kidney has a different substrate specificity since it is inactive towards native or partially desialylated and/or resialylated glycophorin A preparations.…”

N-Glycans carried by Tamm-Horsfall glycoprotein have a crucial role in the defense against urinary tract diseases

“…In our laboratory, it has been shown that β1,4-N-GalNActransferase requires the presence of NeuAc (not NeuGc) α2-3-linked to Gal for its task of adding the immunodominant sugar [84][85][86]. The tissue distribution of this β1,4-N-GalNActransferase (also termed Sd a -transferase and homologous to the murine CT transferase [87]) correlates with the tissue localization of the Sd a antigen, namely, it is particularly abundant in the human kidney and colon, and a soluble form is present in urine from Sd(a+) individuals [88][89][90].…”