文章基本信息

标题：Substrate specificity of rat brain ceramidase
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作者：Samer El Bawab ; Julnar Usta ; Patrick Roddy 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2002
卷号：43
期号：1
页码：141-148
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：In this study, the substrate specificity of a newly identified rat brain ceramidase (CDase) was investigated. To this end, the major functional groups and stereochemistry of ceramide (Cer) were evaluated for their influence on the hydrolysis of substrate by this CDase. The results showed that, of the four possible stereoisomers of Cer, only the natural d -e-C₁₈-Cer isomer was used as substrate ( K_m of 1.1 mol% and V_max of 5 μmol/min/mg). Removal of the 4–5 trans double bond to generate dihydroceramide decreased the affinity of the enzyme toward its substrate by around 90%, whereas changing the configuration of the double bond from the natural trans configuration into cis or introduction of a hydroxyl group (phytoceramide) resulted in loss of hydrolysis. Shortening the chain length of the sphingosine backbone resulted in decreased affinity. Methylation of either the primary or the secondary hydroxyl groups resulted in loss of activity. Results also indicated that Cer species that harbor long saturated or monounsaturated fatty acyl chains are preferred substrates of the enzyme. α-Hydroxylated Cer demonstrated considerably higher affinity, indicating a preference of the enzyme to those Cer molecular species. These results disclose a very high specificity of nonlysosomal CDase for its substrate, Cer. —El Bawab, S., J. Usta, P. Roddy, Z. M. Szulc, A. Bielawska, and Y. A. Hannun. Substrate specificity of rat brain ceramidase. J. Lipid Res. 2002. 43: 141–148.
关键词：nonlysosomal ceramidase ; mitochondrial ceramidase ; ceramide ; dihydroceramide ; hydroxy-ceramide ; stereochemistry