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 Ki than the other isoforms pointing towards the origin of FB1 sensitivity in plants. Overall, the data suggest distinct roles and modes of regulation for each of the ceramide synthases in Arabidopsis sphingolipid metabolism.
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March 2016
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Structure of the alpha1, beta1, gamma1 isoform of AMPK bound to a chlorinated analog of A769662 (‘Cl-A769662’). Alpha colored in purple, beta in blue, gamma in light pink. Cl-A769662 shown in yellow sticks and AMP bound to gamma shown in green sticks. Image kindly provided by Francis Rajamohan (Groton, U.S.A.). - PDF Icon PDF LinkFront Matter
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Research Article|
February 24 2016
Substrate specificity, kinetic properties and inhibition by fumonisin B1 of ceramide synthase isoforms from Arabidopsis
Kyle D. Luttgeharm;
Kyle D. Luttgeharm
*Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, NE 68588, U.S.A.
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Edgar B. Cahoon;
Edgar B. Cahoon
*Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, NE 68588, U.S.A.
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Jonathan E. Markham
Jonathan E. Markham
1
*Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, NE 68588, U.S.A.
1To whom correspondence should be addressed (email jemarkham@unl.edu).
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Publisher: Portland Press Ltd
Received:
July 23 2015
Revision Received:
December 03 2015
Accepted:
December 03 2015
Accepted Manuscript online:
December 03 2015
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 2016 Authors; published by Portland Press Limited
2016
Biochem J (2016) 473 (5): 593–603.
Article history
Received:
July 23 2015
Revision Received:
December 03 2015
Accepted:
December 03 2015
Accepted Manuscript online:
December 03 2015
Citation
Kyle D. Luttgeharm, Edgar B. Cahoon, Jonathan E. Markham; Substrate specificity, kinetic properties and inhibition by fumonisin B1 of ceramide synthase isoforms from Arabidopsis. Biochem J 1 March 2016; 473 (5): 593–603. doi: https://doi.org/10.1042/BJ20150824
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