Isoenzymes of acid phosphatase in germinating peas

Acid phosphatase activity in pea cotyledons increases during germination. Gel filtration separates three isoenzymes with pH optima of 4.9, 5.6 and 6.0. The relative activities of these isoenzymes change during germination. The increase in activity is confined to two of the three isoenzymes. Density-labelling experiments whow that these are synthesised de novo. Activity of the third isoenzyme, which is present in dry seeds, does not change significantly during germination, and is not affected by cycloheximide but is lost on freezing. The possible localization of each isoenzyme is discussed in the light of these findings and in relation to histochemical studies.

Mass spectrometry of lipids. II. Monoglycerides, their diacetyl derivatives and their trimethylsilyl ethers

The mass spectra of 1- and 2-monoglycerides, their diacetyl derivatives and their trimethylsilyl (TMS) ether derivatives were recorded at high (80 eV) and low (6-13 eV) voltages. The fatty acid components of these derivatives included the even-numbered saturated acids from capric to arachidic acid plus oleic, linoleic and linolenic acids. Differences between isomeric 1- and 2-monoglycerides were not sufficient to provide a basis for the analysis of these isomers. Mass spectra of the monoglycerides were very similar to the corresponding methyl esters. Mass spectra of the diacetyl derivatives were qualitatively similar to triglycerides of long-chain fatty acids, but parent ions were not observed. The spectra of diacetyl derivatives may be used for distinguishing 1- and 2-monoglycerides, but the spectra of the TMS ethers are better in this regard. The latter derivatives have fragmentation patterns distinct for the 1- and 2-monoglyceride isomers, particularly at low electron voltages.