| Abstract: | One of the cysteine residues believed to be necessary for reductive light activation is lacking in the only red algal NADP-linked glyceraldehyde-3-P dehydrogenases for which sequences are available, namely Gracilaria verrucosa (Hudson) Papenfuss and Chondrus crispus Stackhouse. Consistent with the mechanism of light modulation proposed for this enzyme, which involves reduction of domain movement-restricting disulfide bonds, it is not reductively activated in Chondrus crispus extracts, and it is not light-activated in whole cells or dithiothreitol (DTT) activated in extracts of the North American species Gracilaria tikvahiae McLachlan. Fructosebisphosphatase and glucose-6-P dehydrogenase, two enzymes for which sequence information from these algae is not yet available, are both activated in crude extracts by DTT treatment, but only fructosebisphosphatase is light-activated in intact Gracilaria. |
