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- Title
Substrate specificity, kinetic properties and inhibition by fumonisin B<sub>1</sub> of ceramide synthase isoforms from Arabidopsis.
- Authors
Luttgeharm, Kyle D.; Cahoon, Edgar B.; Markham, Jonathan E.
- Abstract
Ceramide makes up the acyl-backbone of sphingolipids and plays a central role in determining the function of these essential membrane lipids. In Arabidopsis, the varied chemical composition of ceramide is determined by the specificity of three different isoforms of ceramide synthase, denoted LAG one homologue 1, -2 and -3 (LOH1, LOH2 and LOH3), for a range of long-chain base (LCB) and acyl-CoA substrates. The contribution of each of these isoforms to the synthesis of ceramide was investigated by in vitro ceramide synthase assays. The plant LCB phytosphingosine was efficiently used by the LOH1 and LOH3 isoforms, with LOH1 having the lowest Km for the LCB substrate of the three isoforms. In contrast, sphinganine was used efficiently only by the LOH2 isoform. Acyl-CoA specificity was also distinguished between the three isoforms with LOH2 almost completely specific for palmitoyl-CoA whereas the LOH1 isoform showed greatest activity with lignoceroyl- and hexacosanoyl-CoAs. Interestingly, unsaturated acyl-CoAs were not used efficiently by any isoform whereas unsaturated LCB substrates were preferred by LOH2 and 3. Fumonisin B1 (FB1) is a general inhibitor of ceramide synthases but LOH1 was found to have a much lower K ithan the other isoforms pointing towards the origin of FB 1 sensitivity in plants. Overall, the data suggest distinct roles and modes of regulation for each of the ceramide synthases in Arabidopsis sphingolipid metabolism.
- Subjects
ARABIDOPSIS thaliana genetics; CERAMIDES; ENZYME kinetics; FUMONISINS; BIOCHEMICAL substrates; LIPID synthesis
- Publication
Biochemical Journal, 2016, Vol 473, Issue 5, p593
- ISSN
0264-6021
- Publication type
Academic Journal
- DOI
10.1042/BJ20150824