3.2. Effects of Tris, nicotinic aci

3.2. Effects of Tris, nicotinic acid, glutathione andN:C ratio on PT productionReplacing, omitting or changing the first 4 parameters inTable 1, i.e. Tris, nicotinic acid, glutathione and N:C ratio,did not result in an improvement of total PT production orthe association of PT to the cell and are therefore only brieflydiscussed here:- Replacing Tris by glycerolephosphate [19] or omittingTris entirely did not result in an increased association ofPT to the cell (results not shown).- Replacement of the modulator nicotinic acid by the nonmodulating compound anthranilic acid [7] had no effecton PT production or its association to the cell (resultsnot shown).- Omitting the potentially toxic glutathione resulted ina clearly lower PT production (no data shown). This couldbe due to the lack of the amino acids in glutathione, although there are no data on metabolic breakdown of thiscompound. For glycine this was tested by supplementingthe medium with this amino acid. However, adding0.3 mM glycine instead of glutathione resulted in a 50%reduction of growth rate (no data shown). Glycine is