Substrate specificities of the enzymes of the oleate desaturase system from photosynthetic tissue

In the microsomal fraction from young pea (Pisum sativum L.) leaves, the oleoyl moieties from oleoyl-CoA are principally transferred to the sn-2 position of phosphatidylcholine by oleoyl-CoA:1-acyl-lysophosphatidylcholine acyltransferase. The major product of this acyl transfer is 1-palmitoyl(stearoyl)-2-oleoyl phosphatidylcholine. The 1-palmitoyl(stearoyl)-2-oleoyl phosphatidylcholine is subsequently converted into 1-palmitoyl(stearoyl)-2-linoleoyl phosphatidylcholine by the oleate desaturase complex without equilibrating with the bulk membrane phosphatidylcholine pool. Hence, both the acyl transfer to phosphatidylcholine and the subsequent desaturation of oleoyl moieties occur on the sn-2 position of phosphatidylcholine, and there is also a functional coupling of the acyltransferase and oleate desaturase.

Download Full-text

Substrate specificities of the enzymes of the oleate desaturase system from photosynthetic tissue

Biochemical Journal ◽

10.1042/bj2271031a ◽

1985 ◽

Vol 227 (3) ◽

pp. 1031-1031

Keyword(s):

Substrate Specificities ◽

Oleate Desaturase ◽

Desaturase System

Download Full-text

The control of CTP:choline-phosphate cytidylyltransferase activity in pea (Pisum sativum L.)

Biochemical Journal ◽

10.1042/bj2400837 ◽

1986 ◽

Vol 240 (3) ◽

pp. 837-842 ◽

Cited By ~ 16

Author(s):

M J Price-Jones ◽

J L Harwood

Keyword(s):

Enzyme Activity ◽

Pisum Sativum ◽

Subcellular Distribution ◽

Microsomal Fraction ◽

Control Mechanisms ◽

Stem Tissue ◽

Enzyme Protein ◽

Pisum Sativum L ◽

Ylacetic Acid ◽

Stimulation Of

Several possible control mechanisms for CTP:choline-phosphate cytidylyltransferase (EC 2.7.7.15) activity in pea (Pisum sativum L.) stems were investigated. Indol-3-ylacetic acid (IAA) treatment of the pea stems decreased total cytidylyltransferase activity but did not affect its subcellular distribution. Oleate (2 mM) caused some stimulation of enzyme activity by release of activity from the microsomal fraction into the cytosol, but neither phosphatidylglycerol nor monoacyl phosphatidylethanolamine had an effect on activity or subcellular distribution. A decrease in soluble cytidylyltransferase protein concentrations was found in IAA-treated pea stems, but this was not sufficient to account for all of the decrease in cytidylyltransferase activity. A 50% inhibition of enzyme activity could be obtained with 0.2 mM-CMP, which indicated possible allosteric regulation. Similar inhibition was obtained with 1.5 mM-ATP, but other nucleotides had no effect. The cytidylyltransferase enzyme protein was not directly phosphorylated, and the inhibition with 1.5 mM-ATP occurred with the purified enzyme, thus excluding an obligatory mediation via a modulator protein. The results indicate that the cytosolic form of cytidylyltransferase is the most important in pea stem tissue and that the decrease in cytidylyltransferase activity in IAA-treated material appears to be brought about by several methods.

Download Full-text

Fatty acid elongation by the microsomal fraction from germinating pea (Pisum sativum L.)

Biochemical Society Transactions ◽

10.1042/bst0080120 ◽

1980 ◽

Vol 8 (1) ◽

pp. 120-121

Author(s):

BRIAN R. JORDAN ◽

JOHN L. HARWOOD

Keyword(s):

Fatty Acid ◽

Pisum Sativum ◽

Microsomal Fraction ◽

Fatty Acid Elongation ◽

Pisum Sativum L

Download Full-text

Lipid metabolism in microsomal fraction from photosynthetic tissue. Effects of catalase and hydrogen peroxide on oleate desaturation

Biochemical Journal ◽

10.1042/bj2130249 ◽

1983 ◽

Vol 213 (1) ◽

pp. 249-252 ◽

Cited By ~ 22

Author(s):

D J Murphy ◽

K D Mukherjee ◽

E Latzko

Keyword(s):

Hydrogen Peroxide ◽

Lipid Metabolism ◽

Pisum Sativum ◽

Microsomal Fraction ◽

Inhibitory Effect ◽

Pisum Sativum L ◽

Tissue Effects

On incubation of microsomal fraction from pea (Pisum sativum L.) leaves with ammonium [1-14C]oleate or [1-14C]oleoyl-CoA in the presence of ATP, CoA, Mg2+ and NADH, the major reactions observed were those catalysed by oleoyl-CoA synthetase, oleoyl-CoA thioesterase, oleoyl-CoA:phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase. The reaction catalysed by oleoyl phosphatidylcholine desaturase was specifically inhibited by H2O2, and this inhibitory effect was overcome by catalase (EC 1.11.1.6).

Download Full-text