Stabilizing effects of sucrose–polymer formulations on the activities of freeze-dried enzyme mixtures of alkaline phosphatase, nucleoside phosphorylase and xanthine oxidase

To stabilize two freeze-dried enzyme mixtures, consisting of alkaline phosphatase, nucleoside phosphorylase and xanthine oxidase, the effects of sucrose–polymer (bovine serum albumin, gelatin, dextran, polyethylene glycol and polyvinylpyrrolidone) formulations on the remaining activity of the enzyme mixtures were investigated. The enzyme mixtures were freeze-dried with the additives, and then stored at 25, 40 and 55 °C. The glass transition temperatures (Tg) of the freeze-dried samples were assessed in order to determine their physical stability. The Tg values of sucrose–polymer formulations, with the exception of sucrose–polyethylene glycol, were higher than that of sucrose alone. Comparison of the remaining activities of freeze-dried samples showed that sucrose–bovine serum albumin and/or –gelatin prevented activity loss more effectively than did sucrose. Sucrose–polyethylene glycol showed protective ability equivalent to that of sucrose. On the other hand, sucrose–dextran and/or –polyvinylpyrrolidone diminished the stabilizing effect of sucrose. During storage, sucrose–gelatin prevented gradual activity loss to a much greater degree than did sucrose alone.