微生物蛋白质谷氨酰胺酶的初步分离纯化

Extraction and Purification of Microbial Protein—Glutaminase

蛋白质谷氨酰胺酶可以特异性地水解蛋白质和多肽的谷氨酰胺残基,研究了产吲哚金黄杆菌产生的微生物蛋白质谷氨酰胺酶的代谢曲线和初步的分离纯化。发酵过程中pH升高,氨浓度增加,到14 h时酶活达到最高为0.359 U/mL。发酵液离心去上清液经3 kD滤膜超滤4倍时,纯化倍数和得率都最高。超滤液加入4倍体积无水乙醇沉淀蛋白质,酶的得率最高为72.7%。沉淀用缓冲液复溶后,经过SP-Sepharose Fast Flow离子交换层析分离,得到单一峰。经过多步纯化后酶得率为31.72%,纯化倍数为124倍,经SDS-PAGE电泳鉴定为单一条带,分子量约为20 kD。

Protein glutaminase（PG）is an enzyme that catalyzes the specific hydrolysis of glutaminyl residues in proteins and peptide. The metabolic pattern of Chryseobacterium indologenes in PG synthesis and primary purification of PG were studied. The pH value and ammonia concentration increased during the fermentation. The maximal PG activity reached 0.359 U/mL for 14 hours culture. The efficiency of purification and yield of PG were maximal when culture borth was centrifuged and the supernatant was concentrated for four times by ultrafiltration with 3 kD cut-off membrane. Ultrafiltrate was precipitated by 4 times volumes ethanol and the maximal yield of PG was 72.7%. Precipitated PG by ethanol was dissolved in PBS buffer and further purified by SP-Sepharose Fast Flow ion-exchange chromatography. A single peak was got in elution profile. The final yield of PG was 31.72% and the PG was purified 124 times after multiple purification steps. The purified sample contained a single band in SDS-PAGE and corresponding molecular weight was about 20 kD.