1. IN'IRODUCTION Studies in vitro have shown that the NADP-glyceraldehyde-3-P dehydrogenase activity is enhanced by components indigenous to chloroplasts: low molecular weight effectors and reduced thioredoxin (1-4). We recently showed that, as had been found for chloroplast fructose-1,6-bisphosphatase, the modification cf the milieu constitu tes another way for changing the kinetic properties cf the enzyme (5-7); organic solvents miscible in water (cosolvents) are functional in increasing the NADP-linked activity. Moreover, the increase cf enzyme specific activity correlates with the hydrophobic character cf the respective organic solvent; high concentrations cf cosolvent are required for !lE.Ximal stirrulation when low is the octanollwater rar tition coefficient. These results suggest that slight modifications cf the enzyme hydrophobic interactions have substantial effects in its activity. Tb explore this possibility the enzyme was (i) subjected to treatments aimed at modifying its intramolecular int eract ions , ani (11) analyzed for kinetic changes. In this context we studied on chloroplast glyceraldehyde-3-P dehydrogenase the influence cf salts and detergents that are cften used for perturbing the mlance cf interactions in proteins (8,9). 2. EXPERIMENTAL PROCEDURES
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