~~It is shown that dimethyl 7-isopropyl-5, IO-dimethylheptalene-1,2-dicarboxylate (1) and dimethyl 5,6,8,10-tetramethylheptalene-l,2-dicarboxylate (2) can be resolved via the corresponding mono-acids and with the aid of optically active primary or secondary amines such as I-phenylethylamine or ephedrine into the (-)-(P)-and (+)-(M)-enantiomeres, respectively. Characteristic for the (P)-chirality of the heptalene n-skeleton with C, or pseudo-C, symmetry are two (-)-CE's at the long wavelength region (450-300 nm) followed by at least one intense (+)-CE at wavelengths about or below 300 nm. The absolute configuration of the heptalenes was correlated with the well-established absolute configuration of (+)-(R)-and (-)-(S)-l -phenylethanol.

(10,12,29). Under conditions in which the donor membrane is actively engaged in lipid synthesis, plant lipid transfer proteins have also been shown to catalyze net transfer from the donor to acceptor membrane ( 17). On this basis, it has been proposed that they participate in the transfer of lipids between membranes in intact cells (17). However, this family of proteins is relatively poorly characterized in several respects, and a role in intracellular lipid transport is not established (2).

Three classes of mutants of Arabidopsis thaliana (L.) Heynhold with alterations in starch metabolism were found to have higher levels of leaf amylase activity than the wild type when grown in a 12-hr photoperiod. This effect was dependent upon the developmental stage of the plants and was largely suppressed during growth in continuous light. The various amylolytic activities in crude extracts were separated by electrophoresis in nondenaturing polyacrylamide gels and visualized by activity staining. The increased amylase activity in the mutants wgs due to an up to 40-fold increase in the activity of an extrachloroplast j8-amylase (EC 3.2.1.2). These observations indicate the existence of a regulatory mechanism that controls the amount of (3-amylase activity in response to fluctuations in photosynthetic carbohydrate metabolism. It is paradoxical that fi-amylase appears to be a highly regulated enzyme, but as yet no physiologically relevant function can be assigned to this enzyme due to the absence of starch in the cytoplasmic compartment of leaf cells.One of the few experimental treatments of higher plants that may result in an increase in the rate of photosynthetic CO2 fixation is to remove some of the leaves from plants at the stage during which seeds are developing (1, 2). In many species, this causes an increase in the rate of photosynthetic CO2 fixation in the remaining leaves. The mechanisms that regulate the altered rate of photosynthesis are not known, but they have been suggested to be either a hormonal signal produced by the developing seeds or a metabolic effect of the altered carbohydrate pools that occur in the leaf cells because of an imbalance between synthesis and export of carbohydrate. To investigate this phenomenon, we have previously identified three classes of mutants of Arabidopsis that either lack leaf starch (3, 4), contain reduced levels of starch (5), or have elevated levels of starch. These mutants have substantial alterations in leaf carbohydrate metabolism that may mimic some of the effects of experimentally induced changes in the ratio of carbohydrate-exporting tissue to carbohydrateimporting tissue. However, by contrast with invasive methods, the specificity and stability of the genetic differences between the mutants and the wild type facilitates a detailed analysis of the secondary metabolic responses that are directly associated with carbohydrate metabolism.A previous analysis of a mutant that was unable to synthesize starch because of a lack of chloroplast phosphoglucomutase activity (3) indicated that it had increased leaf sugar content and altered photosynthesis and dark respiration rates, which were secondary effects of an inability to synthesize starch. In a further analysis of the secondary effects of this and related mutations on other aspects of leaf metabolism, we have identified a major effect on the leaf 3-amylase (EC 3.2.1.2) activity in these mutants. Elucidation of the mechanisms responsible for this effect may provide fresh insights into the regulation of l...

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