This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Fatty Acid and Lipids Degradation|
Sphingolipids are ubiquitous cell components present in eukaryotes and bacteria. A sphingolipid molecule is typically composed of a long-chain base (LCB, also known as sphingoid base), an amide linked fatty acyl chain, and a polar head. Ceramides (without a polar head group), glycosylceramides, and glycosylinositolphosphoceramides (GIPCs) are the predominant plant sphingolipids. Sphingomyelin, with phosphocholine as the polar head group, is the major sphingolipid in animals. Yeast contains predominantly inositolphosphoceramides (reviewed in [Lynch04, Pata10].
Some physiological roles of sphingolipids have been determined. Ceramides have been well known as inducers of programmed cell death in animal cells, and the same role was evidenced in plants (reviewed in [Pata10]). In plants, GIPCs are involved in maintaining Golgi and ER integrity, in symbiosis, and function as GPI anchors for proteins (reviewed in [Pata10]). Glycosylsphingolipids play roles in increasing plasma membrane stability, reducing ion permeability and pathogenesis. They were also implicated in chilling and freezing tolerance, as well as drought tolerance in plants (reviewed in [Pata10]). Free LCBs (sphingoids) and phosphorylated LCBs (LCB-Ps, sphingoid 1-phosphates) were implicated as mediators of cellular responses. Like ceramides, LCBs were shown to promote programmed cell death in mammalian and plant cells. LCB-Ps were shown to be signaling intermediates in various cellular responses such as proliferation, differentiation, and cytoskeleton organization (reviewed in [Pata10]).
About This Pathway
Ceramides are degraded by ceramidases. Ceramidases hydrolyze the N-acyl linkage between the long chain bases and the fatty acyl moieties. Ceramidases have been well characterized from human, yeast and a number of other organisms. The only characterized plant ceramidase is a rice ceramidase which however did not act with any of the predominant plant ceramides in vitro [Pata08]. Expressing the rice ceramidase in a yeast mutant increased the yeast endogenous phytoceramide level, which indicated a reverse ceramidase activity of the rice enzyme. The in planta role of this plant ceramidase is unclear. Free long chain bases liberated from ceramides are further degraded into corresponding aldehydes and a phosphorylethanolamine via the intermediate long chain base 1-phosphates.
Tsegaye07: Tsegaye Y, Richardson CG, Bravo JE, Mulcahy BJ, Lynch DV, Markham JE, Jaworski JG, Chen M, Cahoon EB, Dunn TM (2007). "Arabidopsis mutants lacking long chain base phosphate lyase are fumonisin-sensitive and accumulate trihydroxy-18:1 long chain base phosphate." J Biol Chem 282(38);28195-206. PMID: 17635905
Worrall08: Worrall D, Liang YK, Alvarez S, Holroyd GH, Spiegel S, Panagopulos M, Gray JE, Hetherington AM (2008). "Involvement of sphingosine kinase in plant cell signalling." Plant J 56(1);64-72. PMID: 18557834
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