The Action of Calf Brain Sialidase on Gangliosides, Sialoglycoproteins and Sialoglycopeptides

Abstract

In agreement with other investigators it has been shown that endogenous as well as added gangliosides are a substrate for brain sialidase. The release of sialic acid was enhanced in the presence of Triton X-100; this might be due to the action of the detergent on the ganglioside micelles. The sialic acid release from endogenous gangliosides was observed over 48 h and compared with the effect of the sialidase on the endogenous glycoproteins. Though the hydrolysis of sialic acid from gangliosides is much faster in the first hours, after 48 h 40 per cent of the total bound sialic was released from both substrates at pH 4.0 and 37°C.Sialoglycopeptides obtained from brain glycoproteins are also metabolized by the sialidase. No effect of Triton X-100 on this substrate has been observed. From sialoglycopeptides, fractions can be obtained by DEAE-Sephadex A-50 column chromatography with a sialic acid content from 8 to 26 per cent. The fractions with a high sialic acid content were about equally active towards brain sialidase as gangliosides. The results agree with the similar turnover rate observed for the carbohydrate chains from gangliosides and glycoproteins, but are in contrast to the observations of other investigators who have stated that glycoproteins are a poor substrate for brain sialidase. In our experiments bovine and ovine submaxillary mucins and sialyl-lactoses showed only slight activity compared to gangliosides and selected brain sialoglycopeptides.Abbreviations used: O.S.M., ovine submaxillary mucin; B.S.M., bovine submaxillary mucin; ganglioside nomenclature, GM1, GDla, GDlb, GTl, according to SVENNERHOLM (1963).

Removal of N‐acetylneuraminic acid from particulate sialoglycoproteins by endogenous membrane bound neuraminidase in calf brain

“…Also in the absence of the detergent a unique pH value (3.8) for sialoglycoproteins and gangliosides was observed. All this demonstrates, in agreement with HEIJLMAN and ROUKEMA (1972), the likelihood that the same enzyme acts on both sialoglycoproteins and gangliosides, the latter compounds being affected, in our case, at an apparent higher affinity. The activity of membrane bound neuraminidase in the total particulate was 0 7 nmol NANA released/min/mg protein (43.4 nmol/g fresh tissue).…”

“…In fact after only 2.5 h incubation, in the presence of the detergent, the maximum hydrolysis (about 42 per cent) was reached. At this time the endogenous multisialogangliosides proved to be completely transformed, as expected (PRETI et al, 1970; OHMAN et al, 1971; HEIJLMAN and ROUKEMA, 1972), into the neuraminidase resistant monosialoganglioside G M~. Under the conditions used, the non-enzymatic hydrolysis of both sialoglycoproteins and gangliosides proved to be negligible.…”

Occurrence of Sialyltransferase Activity in the Synaptosomal Membranes Prepared from Calf Brain Cortex

“…The occurrence in synaptosomal membranes of sialidase has been definitely assessed (Schengrund and Rosenberg, 1970;Tettamanti et al, 1972). This enzyme also affects the endogenous sialylglycoconjugates (Heijlman and Roukema, 1972;Preti et al, 1973;Tettamanti et al, 1975). Conversely, the presence of sialyltransferase at the synaptic level is, at present, controversial.…”

Studies of the Metabolism of Asialotransferrins: Evidence that Transferrin Does not Undergo Desialylation in Vivo

“…Secondly, neuraminidase is present in a variety of tissues, such as brain (e.g. Roukema & Heijlman, 1970;Schengrund & Rosenberg, 1970;Heijlman & Roukema, 1972), corpus luteum (Unbehaun, 1970), eye (Tulsiani, Nordquist & Carubelli, 1973) (Srivastava, Zaneveld & Williams, 1970).…”