Effect of vitamin B-6 supplementation on degradation rates of short-lived proteins in human neutrophils

Metabolic pathways are controlled primarily by protein degradation rates. D egradation rates, in turn, are controlled by changes in physiologic conditi on 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 b e appropriate cells for assessing protein turnover as affected by macronutr ients 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 uas measured after 30 minutes o f S-35-Met incorporation followed by a 30-minute washout incubation; degrad ation tr as measured after an additional 5-hour incubation. Following prote in separation, radioactive images of short-lived proteins were electronical ly separated into bands. Vitamin B-6 supplementation significantly increase d the synthesis of most neutrophil protein bands. There was a significant d ecrease 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 aspartat e aminotransferase (AC-AST) decreased markedly. There was a significant pos itive correlation between the decrease in AC-AST and protein degradation, T he N-end rule proposes that pyridoxal 5'-phosphate decreases degradation ra tes of short-lived proteins by binding to lysyl residues. A biochemical mod el of the mechanism of cellular protein turnover, as affected by nutritiona l intervention, in human neutrophils is demonstrated. (C) Elsevier Science Inc. 1999. All rights reserved.