Amino Acid Sequences of the Amino-and Carboxyl-Terminal and Reactive Serine Regions of Carboxypeptidase C_Ua

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The amino acid sequences of the amino-and carboxyl-terminal regions of carboxypeptidase C_Ua were determined to be Ala-Val-Glu-Leu-His-Phe-Ile-His-Asn-and-Arg-His-Met-Glu-Pro-(Ala, Asp, Lys)-Gly-Thr-Ser, respectively. The enzyme was inactivated with the incorporation of 1 mol of ³H-labeled diisopropylfluorophosphate (DFP) per mol of enzyme, and this reagent was found to react with a serine residue in the active site of the enzyme. The primary structure around this reactive serine residue was determined to be Asp-Val-Ala-Gly-Tyr-Asp-Ser-Glu-Trp-Ile-Gln-Leu-Arg-Val-Pro-Cys-Glu-Gly-Asp-Ser-Gly-Gly-Glu-Leu-Asp-Lys-Glu-Gly-Met-Ala-Pro-Asn-Gly-Ile-Val-Ser-Asp-Ala-Leu-Phe-Thr-Ser-Arg (Ser, reactive serine) by sequence analysis of two radioactive peptides released from [³H] DFP-treated carboxypeptidase C_Ua on tryptic digestion and cyanogen bromide cleavage.