ABSTRACT
The low content of the essential amino acid l-methionine limits the nutritive value of many food proteins of plant origin. The relative growth-promoting abilities of isomeric methionine dipeptides have been determined by Baker et al. in chicks. The biological utilization of isomeric methionine dipeptides can be discussed in terms of the possible metabolic pathways for the generation of l-methionine. Although N-acetyl-l-methionine is well utilized as a nutritional source of l-methionine in a number of species, including humans, acylation has been shown in pigs to result in a lag in the rise of peripheral plasma methionine. The calcium salts of l and d-a-hydroxy analogues of methionine had potencies of 55.4% and 85.7%, respectively. Several of the analogues were less growth inhibiting or toxic at high concentrations in the diet than was l-methionine. These results imply that some methionine dipeptides or analogues may be better candidates for fortifying foods than l-methionine.
