A Biochemical Lesion of Lysine Deficiency in Man. ∗

Abstract

In a previous report 1 it was shown by nitrogen balance studies that lysine is a dietary essential for man. Observations on the urine were made at that time 2 in lysine-deficient subjects, but with the exception of an increased sulfate excretion no very definite changes were encountered. The present report describes further experiments which have confirmed our previous finding of a negative nitrogen balance and have extended our studies of the urinary constituents in this deficiency. These studies have revealed a striking rise in the non-ketone organic acids of the urine in this deficiency.

The lysine-deficient diets for the 3 subjects in the present study (No. 4 ♀, No. 5 ♂ and No. 6 ♂) were similar to those described in our previous report. The protein moiety was provided by an acid hydrolysate of deaminized casein, supplemented by 1.5% l-tryptophane and 1% l-cystine; this was fed in quantities of 0.1 g N/kg/day. The total caloric intake of the subjects varied from 2400-2700 cals./day. Since these subjects had been accustomed to a somewhat larger nitrogen intake we attempted to avoid the delay in reaching an initial nitrogen equilibrium by maintaining them on a protein-free diet for two days. This was followed by a 4-day control period in which nitrogen was supplied in the quantity mentioned above in the form of a lysine free amino acid mixture which had been supplemented by 6% l (+) lysine. It had been planned to submit the subjects to the lysine-deficient diet for a 24-day period; however, 5 days after this regimen had been instituted, all 3 subjects complained of nausea, dizziness and hypersensitivity to metallic sounds. So objective signs were, however, discovered by clinical examinations. A study of the curves in Fig. 1 reveals that a definite negative nitrogen balance had developed in all three subjects during this brief period.