Purification, characterization, and the complete amino acid sequence of porcine pancreatic deoxyribonuclease

Porcine pancreatic DNase has been purified to homogeneity. The polypeptide exhibits a single band of Mr = 34,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is a glycoprotein containing glucosamine. The results of end group analyses show leucine at the NH2 terminus and alanine at the COOH terminus. The enzymatic properties of the purified porcine DNase are very similar to those of bovine and ovine DNases. The sequence data on the tryptic and chymotryptic peptides derived from CNBr fragments of porcine DNase, along with the results of automated Edman degradation of the intact polypeptide and of the two largest CNBr fragments, indicate the complete amino acid sequence of porcine DNase to be as follows:L-R- I-A-F-N-I-R-T-F-G-E-T-K-M-S-N-A-T-S-N-Y-I-V-R-I-L-S-R-Y-D-I-A-L-I-Q- E-V-R-D-S-H-L-T-A-V-G-K-L-L-N-E-L-N-Q-D-D-P-N-N-Y-H-H-V-V-S-E-P-L-G-R- S-T-Y-K-E-R-Y-L-F-V-F-R-P-N-Q-V-S-V-L-D-S-Y-L-Y-D-D-G-C-E-P-C-G-N-D-T- F-N-R-E-P-S-V-V-K-F-S-S-P-F-T-Q-V-K-E-F-A-I-V-P-L-H-A-A-P-S-D-A-A-A-E- I-N-S-L-Y-D-V-Y-L-N-V-R-Q-K-W-D-L-Q-D-I-M-L-M-G-D-F-N-A-G-C-S-Y-V-T- T-S-H-W-S-S-I-R-L-R-E-S-P-P-F-Q-W-L-I-P-D-T-A-D-T-T-V-S-S-H-T-C-A-Y- D-R-I-V-V-A-G-P-L-L-Q-R-A-V-V-P-D-S-A-A-P-F-D-F-Q-A-A-F-G-L-S-Q-E-T- A-L-A-I-S-D-H-Y-P-V-E-V-T-L-K-R-A. The polypeptide consists of 262 amino acid residues. One of the two disulfide loops links Cys-101 and Cys-104 and the other Cys-173 and Cys-209. Two carbohydrate side chains are attached at Asn-18 and Asn-106.