Biosynthesis of ethylene from methionine. Isolation of the putative intermediate 4-methylthio-2-oxobutanoate from culture fluids of bacteria and fungi

Abstract

Methods are described for identifying the 2,4-dinitrophenylhydrazones of 4-methylthio-2-oxobutanoate by means of t.l.c., n.m.r. and mass spectroscopy. By using these methods 4-methylthio-2-oxobutanoate, a putative intermediate in the biosynthesis of ethylene from methionine, has been identified in culture fluids of Aeromonas hydrophila B12E and a coryneform bacterium D7F grown in the presence of methionine. Relative to 4-methylthio-2-oxobutanoate, the yield of 3-(methylthio)propanal (methional) from the same cultures was less than 1%. Because 4-[2H]methylthio-2-oxobutanoate was obtained from cultures grown on [Me-2H]methionine, the 4-methylthio-2-oxobutanoate must be derived from methionine. By means of t.l.c. alone, 4-methylthio-2-oxobutanoate was identified in the culture fluids of a range of bacteria, the yeast Saccharomyces cerevisiae and the fungus Penicillium digitatum. A photochemical assay developed for 4-methylthio-2-oxobutanoate shows it to be a product of the metabolism of methionine by Escherichia, Pseudomonas, Bacillus, Acinetobacter, Aeromonas, Rhizobium and Corynebacterium species.

Revisiting the methionine salvage pathway and its paralogues

“…While MTA has been discovered as a by-product of ethylene production in plants ( Fig. 1 dotted blue arrows), the existence of similar pathways in microbes is still open to questions (Billington et al, 1979;Fukuda et al, 1989;Miller et al, 2018a). Sometimes linked to methionine, pathways that produce ethylene often do not produce MTA.…”

Ethylene production and toxigenicity of methionine and its derivatives with riboflavin in cultures of Verticillium, Fusarium and Colletotrichum species exposed to light

“…In this, unhke the ACC pathway, methionine is first deaminated to aketo-y-methylthiobutyric acid (KMBA) and then further degraded to ethylene either enzymatically by peroxidases or photochemically in the presence of flavin (Primose 1979, Yang 1967. Billington et al (1979) indicated that most microorganisms are capable of converting methionine to KMBA. It seems likely that the KMBA pathway for ethylene biosynthesis is present in V. dahliae since KMBA served as an excellent substrate for ethylene production.…”

Ethyl 2-[(2,4-difluorophenyl)hydrazinylidene]-3-oxobutanoate

“…Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 (Billington et al, 1979). Some oxobutanoates exhibit cytotoxic properties (Stancho et al, 2008).…”

“…For the biological activity of oxobutanoate derivatives, see: Billington et al (1979); Stancho et al (2008). For the biological activity of pyrazole derivatives, see: Rai et al (2008); Girisha et al (2010); Isloor et al (2009).…”