Showing papers by "John L. Harwood published in 1982"
TL;DR: The hypothesis that the slower senescence changes of the Bf 993 mutant may be due, in part, to an altered membrane lipid composition is supported.
Abstract: The lipid compositions of leaves from Festuca pratensis cv. Rossa (yellowing) were compared with those from a non-yellowing mutant, Bf 993. The leaves of Bf 993 contained a higher level of acyl lipids on both a fresh-weight and a dry-weight basis. Diacylgalactosylglycerol, diacylgalabiosylglycerol and phosphatidylinositol were relatively enriched in the Bf 993 mutant while phosphatidylcholine was relatively reduced. There were no differences in the fatty-acid compositions of individual lipids between the two varieties. During senescence, the lipids of cv. Rossa were progressively degraded over an 8-d period. In contrast little lipid degradation was observed in the Bf 993 mutant during the first 4 d. The results support the hypothesis that the slower senescence changes of the Bf 993 mutant may be due, in part, to an altered membrane lipid composition.
69 citations
TL;DR: The extent and pattern of labelling were not affected by the presence of protein synthesis inhibitors indicating that the enzymes involved in phospholipid synthesis have a rather slow turnover.
44 citations
TL;DR: The role of CoA in controlling fatty acid synthesis in the pea microsomal fraction is discussed and complex lipid labelling was relatively increased while that of acyl-acyl carrier proteins was decreased.
11 citations
8 citations
TL;DR: Although addition of exogenous phospholipases had no effect on total fatty acid synthesis by the soluble fraction, it did increase alpha-hydroxylation of newly-formed palmitate and stearate and provide further evidence for differences between the soluble and particulate fatty acid synthetase andPalmitate elongase activities of germinating pea.
Abstract: 1. The effect of exogenous lipases on fatty acid synthesis from [14C]malonyl-CoA by the microsomal and soluble fractions from germinating peas was studied. 2. Addition of phospholipase A2 or the lipase from Rhizopus arrhizus had no effect on total fatty acid synthesis by the soluble fraction but caused severe inhibition of that by the microsomal fraction. 3. The addition of enzymes with phospholipase activity particularly inhibited the microsomal stearate elongase. 4. Control studies indicated that the phospholipase-induced inhibition of fatty acid synthesis was due to the location of fatty acid synthetase, palmitate elongase and stearate elongase on the outside of the microsomal vesicles. 5. Experiments with a trypsin-like proteinase showed that approximately half the microsomal fatty acid synthesis was resistant to proteolysis. 6. Although addition of exogenous phospholipases had no effect on total fatty acid synthesis by the soluble fraction, it did increase alpha-hydroxylation of newly-formed palmitate and stearate. 7. The results provide further evidence for differences between the soluble and particulate fatty acid synthetase and palmitate elongase activities of germinating pea.
4 citations