HYDROLYSIS OF GALACTOSYLSPHINGOSINE AND LACTOSYLSPHINGOSINE BY BETA-GALACTOSIDASES IN HUMAN-BRAIN AND CULTURED FIBROBLASTS
HYDROLYSIS OF GALACTOSYLSPHINGOSINE AND LACTOSYLSPHINGOSINE BY BETA-GALACTOSIDASES IN HUMAN-BRAIN AND CULTURED FIBROBLASTS
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DOI：
10.1016/0005-2760(87)90103-2
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发表时间：
1987-08-15
期刊：
影响因子：
--
通讯作者：
GOTO, I
中科院分区：
文献类型：
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作者：
GODA, S;KOBAYASHI, T;GOTO, I
Enzymatic properties of .beta.-galactosidases with galactosylsphingosine (psychosine) and lactosylsphingosine as the substrates were examined. Although bile salts were stimulatory on the hydrolysis of the glycolipids in normal brain and cultured fibroblasts, the hydrolytic activities could be readily assayed, without detergents. The in vitro hydrolysis of lactosylsphingosine in cultured fibroblast homogenates was catalyzed by two enzymes, as is the case with the hydrolysis of galactosylceramide and lactosylceramide. Lactosylsphingosine .beta.-galactosidase activities assayed in the absence and the presence of taurocholate (probably lactosylceramidase I) were deficient in fibroblasts from patients with globoid cell leukodystrophy, while the activity assayed with sodium cholate (probably lactosylceramidase II) was deficient in GM1 gangliosidosis fibroblasts. In contrast, galactosylsphingosine .beta.-galactosidase was not activated by cholate and the enzyme activities assayed with the no-additive and taurocholate systems were deficient in brain and fibroblasts from patients with globoid cell leukodystrophy, thereby indicating that the hydrolysis of galactosylsphingosine is catalyzed by one enzyme, galactosylceramidase I. Exogenous lipids and an activator protein purified from normal spleen activated galactosylsphingosine .beta.-galactosidase but they were inhibitory to lactosylsphingosine .beta.-galactosidase. Because the Km values of lactosylsphingosine .beta.-galactosidase assayed with cholate were several magnitude higher than those obtained with the no-additive system and because lactosylsphingosine is readily hydrolyzed with the no-additive system in vitro, it is likely that the in vivo hydrolysis of the lipid is catalyzed by only one enzyme, lactosylceramidase I.
