The specificity of glutamine for growth of Streptococcus haemolyticus)

Abstract

The many glutamine analogues and derivatives tested proved incapable of replacing glutamine in supporting growth of Strep. haemolyticus. Apparently none of these compounds can be converted into glutamine by Strep. haemolyticus at a rate sufficient to meet its demands in even extremely slow growth. Strep. haemolyticus seems to be incapable of such relatively simple operations as forming the [gamma]-amide of glutamic acid, hydrolyzing an N-acetyl, N-leucyl or N-cysteyl grouping, or hydrolyzing peptide linkages between the carboxylic acid grouping of glutamine and the amino groupings of glycine, glutamic acid or cysteine. It also cannot open the rings of pyrrolidone-[alpha]-carboxylic acid or glutamic acid imide by addition of NH3 or water in the necessary positions. Particularly significant in relation to the mode of action of glutamine is the inactivity of the glutamine peptides. It may be argued that if Strep. haemolyticus has no enzyme mechanisms capable of breaking down simple peptides to release glutamine, then, from the normal reversibility of enzyme systems, it is also incapable of building up glutamine into normal peptides. Thus the purpose for which glutamine is used by the organsm is not peptide formation unless enzymes specific to a particular peptide are involved. The inability of Strep. haemolyticus to form unusual amide linkages has been commented on (Mcllwain, 1939). With this reservation, it would appear that glutamine is used by the organisms as such, rather than for building up a larger molecule, as the compounds tested present examples of every likely type of combination with glutamine. A suggestion as to the use of glutamine obvious from its peculiar properties is that of NH3 transference. If glutamine is involved in such a cyclic process, the compounds into which it is converted would be expected to show glutamine activity. Nevertheless, ammonium pyrrolidone-[alpha]-carboxylate, the product of breakdown of glutamine in aqueous soln., is inactive, as also is glutamic acid, the product of action of glutaminase on glutamine.