AMINO ACID SEQUENCE OF BOVINE CARBOXYPEPTIDASE A .I. PREPARATION AND PROPERTIES OF FRAGMENTS OBTAINED BY CYANOGEN BROMIDE CLEAVAGE

Bovine carboxypeptidase Aγ has been subjected to cleavage by cyanogen bromide and the fragments were produced isolated by gel filtration on Sephadex G-75 equilibrated in 0.1 M propionic acid. In addition to the amino- and carboxylterminal peptides previously isolated and characterized, two large fragments, designated FI and FIII, have been obtained. The first of these, FI, occurs mainly as a high molecular weight aggregate in 0.1 M propionic acid while FIII shows little or no aggregation properties but exhibits nonideal behavior. Sedimentation equilibrium analyses in 6 M guanidine hydrochloride show FI to possess a molecular weight about 23,000 and Fm a molecular weight of about 9000. Amino acid analyses of each fragment indicate that FI and FIII are composed of 198 and 81 amino acid residues, respectively. Each fragment contains a single aspartyl residue as amino terminus. The relationship of the four cyanogen bromide fragments of bovine carboxypeptidase Aγ to the primary structure of the enzyme is discussed. © 1969, American Chemical Society. All rights reserved.