2-Methylcitrate dehydratase, a new enzyme functioning at the methylcitric acid cycle of propionate metabolism.

Abstract

2-Methylcitrate dehydratase (2-methylcitrate hydro-lyase), a new enzyme functioning at the methylcitric acid cycle of propionyl-CoA oxidation, was present in the cell-free extract of Yarrowia (Saccharomycopsis) lipolytica. The enzyme was separated from the usual aconitate hydratase (EC 4.2.1.3) of the yeast with DEAE-Sephadex A-50 column chromatography. The enzyme was able to catalyze a reversible reaction between 2-methylcitrate and 2-methyl-cis-aconitate, but showed no activity on threo-ds-2-methylisocitrate, citrate, cis- or trans-aconitate, threo-ds-, threo-DL- or erythro-ls-isocitrate, DL-homocitrate or other hydroxy-acids tested.In contrast, the other enzyme fraction separated as aconitate hydratase by chromatography showed no activity on synthetic 2-methylcitrate, but was able to catalyze strongly a reversible reaction between 2-methyl-cis-aconitate and threo-ds-2-methylisocitrate.From these findings, the previously proposed cycle sequence was revised at the following broken arrows: propionyl-CoA+o...