DIFFERENCES IN THE GLYCOSYLATION OF RAT SUBMANDIBULAR KALLIKREINS

The glycosylations of five different rat submandibular kallikreins, rK 1, rK2, rK7, rK9 and rK10, vacuum-blotted onto nitrocellulose membrane s, have been studied by means of labelled lectins using enhanced chemi luminescence detection. The results demonstrated that individual subma ndibular kallikreins are not heavily glycosylated in rats, but consist ently show different patterns of glycosylation. Following digestion of slot-blotted enzymes with peptide-N-glycosidase F (PNGase): binding b y lectin from Lens culinaris (alpha Man-directed) was abolished, whils t that of lectin from Maclura pomifera (Gal beta 1,3GalNAc-directed) p ersisted (but could be abolished by periodate oxidation and endo-alpha -N-acetylgalactosaminidase digestion), revealing that there are O- as well as N-linked sugar chains on the kallikreins; a novel observation for this family of enzymes. The presence of GalNAc in addition to GlcN Ac, Fuc, Gal and Man, in sugar chains of rK1 was confirmed by high pH anion exchange chromatography following a acid hydrolysis. Different i ntensities of binding by lectin from Limax flavus (NeuNAc-directed) su ggest that sialylation of individual kallikreins differs, whilst siali dase and PNGase digestions suggest that sialic acid is the terminal re sidue of some N-linked but not O-linked structures.