Stability and catalytic activity of α-amylase from barley malt at different pressure–temperature conditions
✍ Scribed by Roman Buckow; Ulrike Weiss; Volker Heinz; Dietrich Knorr
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 224 KB
- Volume
- 97
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
Abstract
The impact of high hydrostatic pressure and temperature on the stability and catalytic activity of α‐amylase from barley malt has been investigated. Inactivation experiments with α‐amylase in the presence and absence of calcium ions have been carried out under combined pressure–temperature treatments in the range of 0.1–800 MPa and 30–75°C. A stabilizing effect of Ca^2+^ ions on the enzyme was found at all pressure–temperature combinations investigated. Kinetic analysis showed deviations of simple first‐order reactions which were attributed to the presence of isoenzyme fractions. Polynomial models were used to describe the pressure–temperature dependence of the inactivation rate constants. Derived from that, pressure–temperature isokinetic diagrams were constructed, indicating synergistic and antagonistic effects of pressure and temperature on the inactivation of α‐amylase. Pressure up to 200 MPa significantly stabilized the enzyme against temperature‐induced inactivation. On the other hand, pressure also hampers the catalytic activity of α‐amylase and a progressive deceleration of the conversion rate was detected at all temperatures investigated. However, for the overall reaction of blocked p‐nitrophenyl maltoheptaoside cleavage and simultaneous occurring enzyme inactivation in ACES buffer (0.1 M, pH 5.6, 3.8 mM CaCl~2~), a maximum of substrate cleavage was identified at 152 MPa and 64°C, yielding approximately 25% higher substrate conversion after 30 min, as compared to the maximum at ambient pressure and 59°C. Biotechnol. Bioeng. 2007;97:1–11. © 2006 Wiley Periodicals, Inc.