Acetylmethylcarbinol Enzyme-System of Aerobacter aërogenes.

Employing the technic of Wiggert, et al., 1 an enzyme-preparation has been extracted from cells of Aerobacter aërogenes, with apparently no hydroclastic activity, nevertheless, capable of converting pyruvic acid into CO₂ and acetylmethylcarbinol. Typical fermentation-balances are shown in Table I. The ratio of pyruvate utilized to CO₂ and acetylmethylcarbinol formed is approximately 2:2:1.

Attempts to increase the carbinol yield by the addition of acetaldehyde were unsuccessful. The added aldehyde was recovered unchanged. If acetaldehyde is an intermediate, only the biologically nascent form is utilized by this enzyme-preparation.

As indicated in Table II no appreciable production of CO₂ and consequently no carbinol occurs at pH levels above 6.8. There is a direct relationship between CO₂ and carbinol production.

The relationship between pH and the direct cleavage of CO₂ from pyruvic acid by Aerobacter will assist in elucidating the mechanism of pyruvate-breakdown. From the investigations of Mickelson and Werkman 2 and from Table II, the carbinol is not formed at alkaline reactions and the predominating mechanism involves reaction I. Under acid conditions both reactions occur. Mickelson 3 has shown that the products of the alkaline fermentation of pyruvate by Aero-bacter are acetic and formic acids in equimolar proportions.