Papaya glutamine cyclase, a plant enzyme highly resistant to proteolysis, adopts an all-β conformation
Papaya glutamine cyclase, a plant enzyme highly resistant to proteolysis, adopts an all-β conformation
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DOI：
10.1046/j.1432-1327.1998.2580214.x
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发表时间：
1998-11-15
期刊：
影响因子：
--
通讯作者：
Looze, Y
中科院分区：
文献类型：
--
作者：
Oberg, KA;Ruysschaert, JM;Looze, Y
谷氨酰胺环化酶催化l-谷氨酰胺肽转化为5-氧丙氨酸肽，同时释放氨。我们在这里报告的生物物理特性的谷氨酰胺环化酶存在于植物木瓜乳汁细胞。纯化至接近均匀性后，该酶进行有限的蛋白水解，并发现其具有较高的抗降解和抗切口性。利用圆二色性和红外光谱分析了这种特性的结构原因。结合木瓜谷氨酰胺环化酶的红外和CD光谱分析、蛋白水解敏感性和氢-氘交换特性，我们得出结论，该蛋白具有广泛的β -片结构，并且可能只有短的固定环连接其β -链。
Glutamine cyclases catalyse the conversion of L-glutaminyl-peptides into 5-oxoprolyl-peptides with the concomitant Liberation of ammonia. We report here biophysical characterisation of the glutamine cyclase present in the laticiferous cells of the plant Carica papaya. After purification to near homogeneity, this enzyme was subjected to limited proteolysis and found to exhibit a high resistance to degradation and nicking. The structural reasons for this property were examined using circular dichroism and infrared spectroscopies. By combining the analyses of the infrared and CD spectra of papaya glutamine cyclase, its susceptibility to proteolysis, and its hydrogen-deuterium exchange characteristics, we conclude that this protein contains extensive beta-sheet structure and is likely to have only short immobile loops connecting its beta-strands.