STRUCTURAL CHARACTERIZATION OF THYMIDINE PHOSPHORYLASE PURIFIED FROM HUMAN PLACENTA

Human thymidine phosphorylase (dThdPase) is thought to be identical to an angiogenesis factor, platelet-derived endothelial cell growth fact or (PD-ECGF). However, the whole amino acid sequence of dThdPase is st ill unknown. N-terminal amino acid sequencing of dThdPase isolated fro m human placenta gave the sequence Ac-AALMTPGTGAPPAPG. Comparison with the sequence predicted from the PD-ECGF cDNA reveals that residues 21 6 of dThdPase are identical to that of PD-ECGF. If dThdPase and PD-ECG F are derived from the same gene, the primary translational product of dThdPase would be processed one amino acid from the translation-initi ating methionine residue and Ala-2 acetylated. Since placental and pla telet PD-ECGF is reported to be processed at Thr-6 and Ala-11, respect ively, and the N-terminal end is not blocked, further study is needed to clarify the reason for this discrepancy and whether the difference in N-terminal sequence affects the physiological function of these mol ecules. (C) 1995 Academic Press, Inc.