THE MICRODETERMINATlON OF FORMATE PRODUCED FROM PYRUVATE BY CELL-FREE EXTRACTS OF ESCHERICHIA COLI *

Previous studies had demonstrated that Furacin (5-nitro-2-furaldehyde semicarbazone) inhibited the dismutation of pyruvate as well as its conversion to acetylmethylcarbinol by cell-free extracts of both avian (1) and bacterial (2) cells. It was therefore thought desirable to investigate the effect of this compound on the so called phosphoroclastic dissimilation of pyruvate to acetyl phosphate and formate by cell-free extracts of Escherichia coli (3). Obviously the most satisfactory method for the study of this reaction would be one by which the amount of formate produced could be determined conveniently and accurately. However, all of the methods described previously for formate analysis are cumbersome and ill-adapted for biochemical studies of this sort, which involve the assay of small amounts of formate, contained in a mixture of other interfering substances. The enzymatic method described here appears to be a highly accurate, relatively simple one for the microdetermination of formate produced from pyruvate by extracts of E. coli, and it should prove useful for the determination of formate in other biochemical preparations. Previous studies by Gale (4) had shown that formate oxidation by cellfree extracts of E. coli was associat,ed with a cytochrome-containing particulate fraction, and later investigations of Sato and Egami (5) had demonstrated that nitrate reduction by whole cells of E. coli was linked to i cytochrome bl, which is contained in the particulate fraction (6). In an atmosphere of Nz, this particulate fraction is capable of mediating the oxidation of formate with the reduction of an equivalent amount of nitrate to nitrite and the production of an equivalent amount of CO2 as shown in the following equation: