α-Aminoisobutyric Acid and Isovaline in Tokyo Bay Sediments

Abstract

Two nonprotein amino acids, 2-amino-2-methylpropionic acid (α-aminoisobutyric acid, αAiBA) and 2-amino-2-methylbutanoic acid (isovaline, iVal) were found in modern Tokyo bay sediments together with several protein amino acids. Concentrations of the two nonprotein amino acids were approximately 1 nmol per g of dry sediment, and the protein amino acids were several hundred to slightly over one thousand nmol per g. iVal was found to be nearly racemic, whereas the protein amino acids were predominantly in the l-form. We do not consider the two nonprotein amino acids to be of extraterrestrial origin as suggested by the study of the Cretaceous/Tertiary (K/T) boundary sediments at Stevns Klint ( Zhao and Bada 1989) and propose a terrestrial origin. The source of the two nonprotein amino acids is not biological because the iVal is racemic. They may come from industrial waste water containing C-5 substituted hydantoins which then hydrolyzed to give αAiBA and racemic iVal.