RESUMO
In our early study [2] labelled formaldehyde, glyoxylate, glycine and serine were formed from 14CO2 during 1 min incubation. Continuing the detailed work by unlabelled HCO3- with short (1 min) incubation time in numerous experiments, there were significant changes in the amount of formaldehyde, glyoxylate, glycine and serine. The main product was glycine. In illuminated leaves after HCO3- intake, the formaldehyde content increased. However, in dark in the presence of 5 mM HCO3- the formaldehyde content decreased and the amount of glyoxylate, glycine and serine increased in green leaves. The transamination is improbable as the amount of glutamate and aspartate did not decrease during the glycine and serine formation. The change in the amount of the measured free amino acids and glyoxylate was hindered by (aminooxy)acetic acid (AOA) and amethopterin. AOA, which is an inhibitor of pyridoxal phosphate has no effect on formaldehyde alteration. In the presence of amethopterin which inhibits the activity of tetrahydrofolate the formaldehyde amount increased in dark kept CO2 containing green leaves instead of decreasing. This shows that tetrahydrofolate has a role in glyoxylate formation from formaldehyde and CO2. A direct formation of glycine and serine can be supposed in definite circumstances during photosynthesis, in which pyridoxal phosphate has an important role.