Effect of vitamin B6 supplementation on degradation rates of short-lived proteins in human neutrophils

Metabolic pathways are controlled primarily by protein degradation rates. Degradation rates, in turn, are controlled by changes in physiologic condition or nutrient supply. Vitamin B(6) is associated with a greater variety of reactions than most other vitamins. Moreover, the vitamin B(6) needs of the elderly tend to be higher than those of young adults. Neutrophils seem to be appropriate cells for assessing protein turnover as affected by macronutrients and micronutrients. Thus, we assumed that vitamin B(6) supplementation, particularly in an elderly population, would change the turnover rates of the neutrophil proteins. Protein synthesis was measured after 30 minutes of (35)S-Met incorporation followed by a 30-minute washout incubation; degradation was measured after an additional 5-hour incubation. Following protein separation, radioactive images of short-lived proteins were electronically separated into bands. Vitamin B(6) supplementation significantly increased the synthesis of most neutrophil protein bands. There was a significant decrease of 25 to 66% in the degradation rates of 235 protein bands. We even detected by statistical evaluation a 20% decrease in the degradation rates of distinct protein bands. Activation coefficients of erythrocyte aspartate aminotransferase (AC-AST) decreased markedly. There was a significant positive correlation between the decrease in AC-AST and protein degradation. The N-end rule proposes that pyridoxal 5'-phosphate decreases degradation rates of short-lived proteins by binding to lysyl residues. A biochemical model of the mechanism of cellular protein turnover, as affected by nutritional intervention, in human neutrophils is demonstrated.