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Literature summary for 2.3.1.24 extracted from

  • Luttgeharm, K.D.; Cahoon, E.B.; Markham, J.E.
    Substrate specificity, kinetic properties and inhibition by fumonisin B1 of ceramide synthase isoforms from Arabidopsis (2016), Biochem. J., 473, 593-603 .
    View publication on PubMed

Cloned(Commentary)

Cloned (Comment) Organism
gene LAG2, recombinant expression of codon-optimized LAG2 as N-terminally FLAG-tagged enzyme in Saccharomyces cerevisiae membranes Arabidopsis thaliana

Protein Variants

Protein Variants Comment Organism
additional information complementation of the growth defect of DELTAlag1/DELTAlac1 yeast deletion mutant by recombinant GST-/FLAG-tagged LOH2. Complementation with LOH2 leads to the accumulation of C16-containing inositolphosphoceramides and ceramides indicating this isoform's preference for C16 fatty acids. Microsomes isolated from LOH2 overexpressing plants showed high levels of C16-ceramide synthase activity compared to microsomes from wild-type plants, indicating that LOH2 overexpression results in accumulation of functional enzyme Arabidopsis thaliana

Inhibitors

Inhibitors Comment Organism Structure
fumonisin B1 mixed mode of inhibition with respect to the long-chain base Arabidopsis thaliana

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
additional information Michaelis-Menten kinetics Arabidopsis thaliana
0.023
-
sphinganine pH 7.5, 30°C, LOH2 Arabidopsis thaliana

Localization

Localization Comment Organism GeneOntology No. Textmining
microsome
-
Arabidopsis thaliana
-
-

Metals/Ions

Metals/Ions Comment Organism Structure
Ca2+ activates Arabidopsis thaliana
Mg2+ activates at 2 mM Arabidopsis thaliana
Mn2+ activates Arabidopsis thaliana
additional information poor effect observed by 0.001 mM of Cu2+, Zn2+, or Co2+ Arabidopsis thaliana

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
palmitoyl-CoA + sphinganine Arabidopsis thaliana
-
CoA + N-palmitoylsphinganine
-
?
palmitoyl-CoA + sphingosine Arabidopsis thaliana
-
CoA + N-palmitoylsphingosine
-
?

Organism

Organism UniProt Comment Textmining
Arabidopsis thaliana Q9LJK3
-
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
additional information specificity of three different isoforms of ceramide synthase, denoted LOH1, 2 and 3, for a range of long-chain base (LCB) and acyl-CoA substrates. The contribution of each of these isoforms to the synthesis of ceramide is investigated by in vitro ceramide synthase assays, overview. The plant LCB phytosphingosine is efficiently used by the LOH1 and 3 isoforms, with LOH1 having the lowest Km for the LCB substrate of the three isoforms. In contrast, sphinganine is used efficiently only by the LOH2 isoform. Acyl-CoA specificity is also distinguished between the three isoforms with LOH2 being almost completely specific for palmitoyl-CoA, while the LOH1 isoform shows greatest activity with lignoceroyl- and hexacosanoyl-CoA. Unsaturated acyl-CoAs are not used efficiently by any isoform while unsaturated LCB substrates are preferred by LOH2 and 3. LOH2 shows poor activity with phytosphingosine. LOH2 is unable to use any acyl-CoA substrates greater than C18 and shows very strong preference for C16 acyl-CoA. Recombinant LOH2 shows maximum activity with the d18:1(4E) LCB about 6 times that with the d18:0 LCB, eventhough d18:1(4E) is not observed in Arabidopsis leaves. Rather d18:2(4E/8Z) or d18:2(4E/8E) are found in selected tissues such as pollen. LOH2 shows enhanced activity towards DELTA4 unsaturated LCB substrates Arabidopsis thaliana ?
-
?
palmitoyl-CoA + sphinganine
-
Arabidopsis thaliana CoA + N-palmitoylsphinganine
-
?
palmitoyl-CoA + sphingosine
-
Arabidopsis thaliana CoA + N-palmitoylsphingosine
-
?

Synonyms

Synonyms Comment Organism
ceramide synthase
-
Arabidopsis thaliana
LAG1 longevity assurance homolog 2
-
Arabidopsis thaliana
LAG12
-
Arabidopsis thaliana
LOH2
-
Arabidopsis thaliana

Temperature Optimum [°C]

Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
30
-
assay at Arabidopsis thaliana

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
7.5
-
assay at Arabidopsis thaliana

Ki Value [mM]

Ki Value [mM] Ki Value maximum [mM] Inhibitor Comment Organism Structure
0.00097
-
fumonisin B1 pH 7.5, 30°C, LOH2 Arabidopsis thaliana

General Information

General Information Comment Organism
physiological function distinct roles and modes of regulation for each of the ceramide synthases in Arabidopsis thaliana sphingolipid metabolism. Ceramides are organizing components of sphingolipids in the eukaryotic cell. Three ceramide synthase isoforms are found in Arabidopsis thaliana each with specific substrate preferences and sensitivity to inhibitors and activators, overview. Isozyme LOH2 is required for the synthesis of ceramides with dihydroxy-long-chain bases and C16 fatty acids Arabidopsis thaliana