Amino acid composition and terminal residues of aspartate aminotransferase from ox heart

1. The amino acid composition of highly purified aspartate aminotransferase from ox heart was determined. 2. Alanine is the only N-terminal residue. 3. Leucine was identified as the only C-terminal residue. 4. No disulphide bridges are present in the enzyme molecule. 5. The thiol groups are not equally accessible, the accessibility being comparatively easier in the apoenzyme molecule.     

Amino acid composition of triticale gluten

The study of the amino acid composition of tritikale gluten has demonstrated that in comparison with that of grain protein it contains much less aspartic acid (by 28.1%) and lysine (by 19.4%), less alanine and arginine but more tyrosine (by 39.7%), glutamic acid (by 31.4%), phenylalanine (by 23.6%) and leucine (by 14.4%) and slightly more threonine and valine. The study has shown no significant differences in the amino acid composition of grain protein and tritikale gluten of different varieties and cultivation regions.     

Amino acid composition of zein molecular components

Zein extracted from maize endosperm has been fractionated into four polypeptide chains, having the following MWs 23 000, 21 000, 13 500 and 9600. By amino acid analysis the two smaller MW chains (representing 30% of total zeins) have been found to be zein-type molecules. These two chains are thought to be responsible for zein granule formation via -S-S- bridges. Zein is also highly heterogeneous in charge, and is resolved into at least 15 components, with pI's in the pH range 5–9. As demonstrated by amino acid analysis, part of this heterogeneity is due to spot mutations in some of the genes responsible for zein synthesis.