Amino acid sequence studies on sheep liver fructose-bisphosphatase. I. The S-peptide.

Fructose-bisphosphatase has been isolated from sheep liver using affinity-elution chromatography from carboxymethylcellulose as the final purification step. The purified enzyme was homogeneous by disc gel electrophoresis. Digestion with subtilisin yielded the N-terminal S-peptide similar to that reported for the rabbit and pig. The peptide has an acetylated amino terminal residue and the following sequence deduced from a study of the tryptic and cyanogen bromide peptides: Ac-Thr-Asp-Glu-Ala-Pro-Phe-Asp-Thr-Asn-Ile-Val-Thr-Val-Thr-Arg-Phe-Val-Met-Glu-Glu-Gly-Arg-Lys-Ala-Arg-Gly-Thr-Gly-Glu-Met-Thr-Gln-Leu-Leu-Asn-Ser-Leu-Cys-Thr-Ala-Val-Lys-Ala-Ile-Ser-Thr-Ala-Val-Arg-Lys-Ala-Gly-Ile-Ala-His-Leu-Tyr-Gly-Ile-Ala. The sheep liver S-peptide sequence shows only six changes in 60 residues and three changes in 56 residues compared with the sequences of the rabbit and pig S-peptides respectively.