Inhibition of Streptomyces griseus aminopeptidase and effects of calcium ions on catalysis and binding - Comparisons with the homologous enzyme Aeromonas proteolytica aminopeptidase
G. Papir et al., Inhibition of Streptomyces griseus aminopeptidase and effects of calcium ions on catalysis and binding - Comparisons with the homologous enzyme Aeromonas proteolytica aminopeptidase, EUR J BIOCH, 258(2), 1998, pp. 313-319
Streptomyces griseus aminopeptidase is a zinc metalloenzyme containing 2 mo
l zinc/mol protein, similar to the homologous enzyme Aeromonas proteolytica
aminopeptidase. In addition, a unique Ca2+-binding site has been identifie
d in the Streptomyces enzyme, which is absent in the Aeromonas enzyme. Bind
ing of Ca2+ enhances stability of the Streptomyces enzyme and modulates its
activity and affinity towards substrates and inhibitors in a structure-dep
endent manner. Among the three hydrophobic 4-nitroanilides of alanine, vali
ne and leucine, the latter displays the largest overall activation (increas
e in k(cat)/ K-m). Large enhancements in affinity (1/K-i) upon Ca2+ binding
have been observed for inhibitors with flexible (leucine-like) residues at
their N-termini and smaller enhancements for inhibitors with rigid (phenyl
alanine-like) residues.