ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract— Activities of rat brain galactosylsphingosine (psychosine) and galactosylceramide (galactocerebroside) galactosyl hydrolases were compared using several criteria. Aqueous homogenates of rat brain were extracted at -30°C with a mixture of ether-methanol (3:1, v/v). This procedure eliminated most of endogenous galactosylceramide and improved the linearity of the enzymatic reaction without inactivating the enzyme. The thermostability of both enzymes was identical while the reference 4-methylumbelliferyl β-galactosidase was less thermostable. The enzymes, solubilized from the ether-methanol powder, were quantitatively precipitated in the combined ammonium sulphate fractions of 20–30% and 30–40% saturation. DEAE-cellulose column chromatography gave identical elution patterns for the two enzymes, with a single major and two minor peaks. Electrofocusing of the major activity peak, obtained from the DEAE-cellulose column, produced a sharp single peak of galactosylsphingosine- and galactosylceramidehydrolysing activities at an isoelectric point of pH 4.45. Developmental changes of these enzymes were identical, showing the most rapid rise concomitant with the period of active myelination. During development, at different purification steps, and in different organs, the ratio of the activities of galactosylsphingosine and galactosylceramide galactosyl hydrolases was relatively constant. While none of these criteria provides definitive proof of identity, they collectively suggest strongly that a single enzyme might catalyse hydrolysis of both galactosylsphingosine and galactosylceramide.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1974.tb11584.x
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