Mechanistic studies on carboxypeptidase A from goat pancreas Part I: Role of tyrosine residue at the active site.

ABSTRACT

Chemical modification of carboxypeptidase Ag1 from goat pancreas with Nacetylimidazole or iodine led to loss of enzymic activity. This loss in activity could be prevented when chemical modification was carried out in the presence of β-phenylpropionic acid or substrate NCbz-glycyl-L-phenylalanine, thus suggesting a tyrosine residue at the active site. Chemical modification of tyrosine was confirmed by spectral and kinetic studies. While tyrosine modification destroyed peptidase activity, esterase activity of the enzyme remained unchanged thus indicating non-involvement of tyrosine residue in ester hydrolysis.