Methylglyoxal: Enzyme distributions relative to its presence in Douglas-fir needles and absence in Douglas-fir needle callus

Abstract Methylglyoxal was isolated as its 2,4-dinitrophenylosazone from an insoluble fraction from Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco] needles but was not observed in a similar Douglas-fir needle callus preparation. This result was consistent with the distribution of enzymes of methylglyoxal metabolism between needles and needle callus. Only catabolic glyoxalases and methylglyoxal reductase could be found in the needle callus, whereas extracts of needles of various ages contained methylglyoxal synthetase and methylglyoxal reductase in a manner suggestive of a function for methylglyoxal in needle development and maturation. While glyoxalases I and II were active in all callus clones tested, activities of these enzymes were not immediately evident in needle extracts. However, it was demonstrated that at least small amounts of glyoxalase I occurred in needle extracts in an inhibited state. From the viewpoint that mature needles and needle callus represent resting and proliferative cellular states, respectively, the data indicate that methylglyoxal may be operating in conifers as a cell division inhibitor as envisioned by Szent-Gyorgyi.