Unraveling the Nutritional Significance of Essential Amino Acids through Synthesis Cost and Cellular Allocation

Abstract

In human clinical nutrition, it is broadly accepted that essential amino acids are critical for muscle and other body protein synthesis. However, the connection between humans’ loss (or cessation) of biosynthesis for these amino acids and their nutritional significance remains largely unexplained. Interestingly, observations in plants—which can produce all 20 proteinogenic amino acids—indicate that supplementation with amino acids deemed essential to humans inhibits plant growth, whereas most nonessential amino acids do not. More precisely, this growth-inhibitory effect corresponded solely to amino acids that are ‘high-cost’ in terms of biosynthesis.

These findings formed a key basis for the hypothesis developed here. By integrating them with prior research on “Economical Evolution” in bacteria and my subsequently proposed “Differential Recycling Efficacy Framework,” I present an additional inference: high-cost amino acids tend to be more abundant in cytoplasms where resource recovery is easier, and this cellular allocation drives their role as triggers for cytoplasmic protein synthesis. This hypothesis speculates that the reason plant growth is inhibited by high-cost amino acids is that, although plants need to break down nutrients stored during the day at night for their growth, externally supplied high-cost amino acids may suppress the plant's protein degradation process.

This new hypothesis, termed the Allocation-Derived Significance Hypothesis, posits that an amino acid’s biosynthetic cost determines its nutritional role via its cellular and subcellular allocation. Since this cellular-allocation-based concept of nutrition is novel, it may offer a fresh perspective in the life sciences and provide new insights for clinical nutrition.