Physiological role of a novel protein disulfide isomerase present in rice endosperm tissue

结果表明，一个表观分子量为40 kDa的PDI 2;3在水稻胚乳组织中对分子间S-S键的形成起着重要的生理作用。通常11 S球蛋白具有分子内S-S键合，其由PDI 1催化;1.表观分子大小为60 kDa。而PDI 2; 3具有较小的40 kDa表观分子大小，不具有分子内S-S键形成酶的功能。水稻胚乳组织中含有酸溶性谷蛋白和醇溶性醇溶谷蛋白两种贮藏蛋白。众所周知，谷蛋白前体在进入液泡之前形成了分子内的S-S键。然而，尚不清楚醇溶谷蛋白聚集体是如何形成的，并在ER腔中积累形成PBI。最后，PDI 2;3作为酶在醇溶谷蛋白多肽之间形成分子间S-S键，并使醇溶谷蛋白聚集形成PBI。

It was elucidated that a nobel PDI2;3 with 40 kDa apparent molecular size plays a physiological role for inter-molecular S-S bond formation in rice endosperm tissue. Generally 11S globulin has intramolecular S-S bonding which is catalysed by PDI1;1. with 60 kDa apparent molecular size. However PDI2;3with small 40 kDa apparent molecular size does not function as intramolecular S-S bond forming enzyme. In rice endosperm tissue there are two types of storage proteins such as acid-soluble glutelin and alcohol-soluble prolamin. It has been well known that an intramolecular S-S bonding of proglutelin is formed before being transporting into vacuole. However it has not been known how prolamin aggregate are formed and are accumulated in ER lumen to form PBI. Finally PDI2;3 functions as an enzyme to form intermolecular S-S bond between prolamin polypeptides and which become prolamin aggregate to form PBI.