May enzyme activity in urine play a role in kidney stone formation?

It has been found that calcium oxalate stone formers have low UGOT and UGPT activity compared to healthy individuals. The urine of 23 stone formers and 19 controls has been tested for combined UGOT and UGPT activity. The effect of L-aspartic acid, alanine and L-glutamic acid on calcium oxalate precipitation has been tested. Only L-glutamic acid exerted a significant retardation effect at physiological concentrations. As GPT and GOT convert alanine and aspartic acid respectively into glutamic acid, a possible mechanism of retardation of kidney stone formation involving enzyme steps via glutamic acid creation in situ is suggested.