Polypeptide possessing protein disulfide isomerase activity gene encoding the same and process for producing the same

Abstract

A highly thermostable polypeptide possessing protein disulfide isomerase (PDI) activity, a gene coding for the polypeptide and a process for producing the polyeptide are provided. The polypeptide possessing PDI activity is characterized by A) having a capability of catalyzing a disulfide exchange in proteins, B) recognizing mainly ribonuclease A as a substrate, C) having a suitable active temperature of 20.degree. to 70.degree. C., D) being stable at a pH value of 6 to 9, and E) having a molecular weight of about 60,000 to 62,000. Since it has a higher thermostability and exhibits a stable activity in a wider dithiothreitol concentration range as compared with the conventional PDI, it is possible to provide a novel enzyme active protein which can be advantageously used for a refolding reaction of certain proteins. Further, a process which enables the polylpeptide possessing PDI activity to be efficiently produced using Humicola insolens or a transformant transformed with an expression vector containing the above-described gene is also provided.

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