Glass transition and thermal stability of lactase in low-moisture amorphous polymeric matrices
Glass transition and thermal stability of lactase in low-moisture amorphous polymeric matrices
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DOI：
10.1021/bp9700014
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发表时间：
1997-03-01
影响因子：
2.9
通讯作者：
Chirife, J
中科院分区：
文献类型：
--
作者：
Mazzobre, MF;Buera, MD;Chirife, J
研究了一种商品化的中性乳糖酶(β-半乳糖苷酶)在不同温度(T)下储存的低水分麦芽糊精和聚乙烯吡咯烷酮无定形聚合物基质中的热稳定性。主要目的是分析玻璃化转变温度(T-g)作为预测乳糖酶在低水分玻璃形成基质中热稳定性的有效性。在玻璃态条件下(无论是在PVP或MD基质中)储存过程中观察到酶活性的丧失，这表明尽管在玻璃态下分子的流动性可能显著降低，但蛋白质分子仍然具有足够的流动性而导致酶失活。结果表明，如果仅根据基质的物理变化来预测，则包埋酶的PVP基质从玻璃态到橡胶状态的变化并不像预期的那样反映在热失活率的温度依赖关系中。在加热的低水分非晶态体系中考虑酶的稳定性时，水的塑化效应并不是唯一要考虑的因素。
The thermal stability of a commercial preparation of neutral lactase (beta-galactosidase) in low-moisture amorphous polymeric matrices of maltodextrin (MD dextrose equivalent (D.E.) = 10.9) and polyvinylpyrrolidone (PVP; MW 40.000) stored at various temperatures (T) was studied. The main objective was to analyze the usefulness of the glass transition temperature (T-g) as a parameter for predicting the thermal stability of lactase in low-moisture glass-forming matrices. Loss;of enzyme activity was observed during storage in glassy conditions (either in PVP or MD matrices), suggesting that, although molecular mobility may be significantly decreased in the glassy state, the protein molecule is still mobile enough to lead to enzyme inactivation. The results indicated that the change from the glassy to the rubbery state of the PVP matrix, where the enzyme was embedded, was not reflected in drastic changes in the temperature dependence of the thermal inactivation rate, as expected if it could be only predicted on the basis of physical changes of the matrices. The plasticizing effect of water is not the only factor to take into account when considering enzymatic stability in heated low-moisture amorphous systems.