On the role of long-chain aldehydes in the light reaction in Photobacterium phosphoreum enzyme preparations

Abstract

1. (1) Active luciferase-DPNH-oxidase preparations from Photobacterium phosphoreum generally contain some aldehyde-attacking enzyme, probably ADH. Under the experimental conditions applied this enzyme appears to attack decanal, but not palmital.

2. (2) The presence of long-chain aldehydes in the enzyme preparations could be demonstrated. It was not possible to establish with certainty that the substance that is active in the light reaction catalyzed by enzyme preparations without added aldehyde is a long-chain aldehyde.

3. (3) There is no experimental evidence for the conversion of palmital in the light reaction.

4. (4) Extraction of enzyme preparations of Ph. phosphoreum with iso-octane increases the light reaction; it seems probable that an inhibitor of luciferase is removed. Palmital, added to the enzyme preparations, is only slightly extracted by iso-octane.

5. (5) The extent of the light reaction in the enzyme preparations extracted with iso-octane depends on the sequence of addition of palmital, DPNH and FMN; the highest reaction is obtained if palmital is added first. The effect is influenced by aldehyde- and FMN concentrations; it is less conspicuous in non-extracted preparations.

6. (6) The experimental facts can be explained if it is assumed that palmital (or a long-chain aldehyde very similar to palmital) serves as a binding agent between the protein and FMNH. The possibility of a second, direct attachment of FMNH to the protein is discussed.