✦ LIBER ✦

Species differences in substrate specificity of pyrimidine nucleoside phosphorylase

✍ Scribed by Yoshihiko Maehara; Yoshihisa Sakaguchi; Tetsuya Kusumoto; Hiroki Kusumoto; Keizo Sugimachi

Publisher: John Wiley and Sons
Year: 1989
Tongue: English
Weight: 280 KB
Volume: 42
Category: Article
ISSN: 0022-4790
DOI: 10.1002/jso.2930420311

No coin nor oath required. For personal study only.

✦ Synopsis

To compare the activity of pyrimidine nucleoside phosphorylase (PNP), an enzyme involved in the metabolism of 5-fluorouracil (5-FU), we used uridine (Urd), deoxyuridine (dUrd), and thymidine (dThd) as substrates and human, rat, and mouse neoplastic and normal tissues. As PNP activity was higher in the tumor tissues than in the normal ones in all species examined, the level of PNP activity is expected to be one critical factor linked to the effectiveness of S-FU. In rats and mice, the ratio of the activities of Urd, dUrd, and dThd was about 10:7: 1, whereas in humans, the ratio was 1:30:20. The main enzyme of PNP is Urd phosphorylase in rodents and dThd phosphorylase in humans. Therefore, when examining the metabolism of S-FU and its analogues for potential clinical application, human tissues should be used.

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