Amino acid composition of elastin in the developing human aorta

Abstract

Elastin was prepared by alkali extraction of defatted human thoracic aortas from 14-, 23-, and 33-week-old fetuses and individuals aged 5 months and 1, 5, 10 and 51 years. The content of lysine decreased and that of desmosines and lysinonorleucine increased most markedly in fetal elastin. Several unknown ninhydrin-positive substances emerged in the basic region of the chromatogram. Two of these unknowns, eluted just after lysine, were incompletely resolved from each other and together comprised 9.6 residues per 1000 total residues in 14-week fetal elastin, decreasing to 8.3 at 23 weeks, to 2.5 residues at 33 weeks, and thereafter were present only in traces. Tyrosine increased in fetal elastin from 7.2 residues at 14 weeks to 11 at 23 weeks and to the adult level of 19 at 33 weeks. Certain other polar amino acids appeared to decrease in elastin with age. Individual variation in the amino acid composition of elastin appears to reside mainly in the relative proportions of glycine, alanine, and proline which make up exactly two-thirds of the total residues.