Effects of illumination and oxygen supply upon the levels of pyridine nucleotides in Chlorella cells

Abstract

1.1. Using intact cells of Chlorella, investigations were made on the effect of light on the levels of various forms of pyridine nucleotides, compared with that on the photogenic reducing agent (R).2.2. No form of pyridine nucleotide was found of which the concentration was affected in the same manner as that of R, which has been known to be produced only in the light and eliminated completely in the dark.3.3. Under both aerobic and anaerobic conditions, light decreased the level of DPN+ and increased the level of TPN. Quantitatively, there was a correspondence between these effects.4.4. When algal cells were transferred in the dark from anaerobic to aerobic conditions, a marked decrease of DPNH occurred, the levels of DPN+, TPN+ and TPNH remaining almost unchanged. The decrease of DPNH in the light (in N2) was assumed to be brought about by the O2 produced concomitantly with the photogenic formation of R and effecting the transfer of DPNH to some substance other than DPN+.5.5. It was concluded that (a) neither TPNH nor DPNH is the primary R and that (b) one of the effects caused by light is the conversion of DPN+ to TPN.