Carboxypeptidase B from human pancreas

Carboxypeptidase B is mapped to human chromosome 3q24. Carboxypeptidase B belongs to A/B subfamily of carboxypeptidases.

Carboxypeptidase B from Sigma has been used as a reference for assaying carboxypeptidase activity in lysed pituitary granules derived from the anterior and intermediate lobes of rat. The enzyme has also been used to digest plasma samples by removing C-terminal basic amino acids, to get a distinct band for each allotype during C4 electrophoresis.

Carboxypeptidase B (or peptidyl-L-lysine (-L-arginine) hydrolase) catalyzes the hydrolysis of the basic amino acids, lysine, arginine, and ornithine from the C-terminal position of polypeptides. It has been shown to be a single polypeptide of 34,000 Da. Trypsin is capable of converting native enzyme to the active enzyme, carboxypeptidase B II in vitro. The optimum pH is found to be 9.0. The enzyme may be used for sequence analysis by successive cleavage of C-terminal basic amino acids. It can also be used as a serum marker for the diagnosis of acute pancreatitis.

Mutations in the carboxypeptidase B (CPB1) gene is implicated with increased susceptibility to pancreatic cancer development and progression. Elevated levels of CPB1 is associated with low grade breast tumors and lymph node positive grade 1 tumors.

One unit will hydrolyze 1 μmole of hippuryl-L-arginine per minute at pH 7.7 at 25 °C

Solution in 0.05 M NaOAc pH 5.0 + 1.0 M NaCl + 0.01% NaN₃