Studies on brunescent cataracts. I. Analysis of free and protein bound amino acids

The concentrations of free amino acids and the composition of protein-bound amino acids have been determined from normal human lens and from human brunescent cataracts. The concentrations of free amino acids are markedly and consistently reduced in brunescent lenses. Little change is found in the amino acid composition of either the soluble or water-insoluble proteins when normal and brunescent lenses are compared. Low concentrations of kynurenine were present in all lens protein hydrolysates and in the free amino acid pool. There appeared to be no significant decrease in protein-bound tryptophan in the brunescent lens.