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ISSN 1672-9145 Acta Biochim Biophys Sin 2004, 36(9): 583–588 CN 31-1940/Q

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The Role of Propeptide in the Refolding of Human Group IB Phospholipase A₂

Hong-Qiang CHENG¹ and Gen-Jun XU^1,2*

¹Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; ²College of Life Science, Zhejiang University of Sciences, Hangzhou 310033, China

Abstract Human group IB phospholipase A2 (IB-PLA2) and its zymogen (proIB-PLA2) were purified from E. coli. Refolding was carried out by diluting the denatured forms of both IB-PLA2 and proIB-PLA2 with renaturation buffer in which the disulfide bonds were completely reduced. The refolding yield of proIB-PLA2 was increased by about 50% over that of the mature enzyme. The refolding of IB-PLA2 usually produced aggregates under normal conditions, as determined by light scattering. In addition, the unfolding experiments showed that the mature enzyme was more stable than the proenzyme toward denaturants in the presence of DTT. Results suggested that the N-terminal sequence rather than its conformation of human proIB-PLA2 played an important role in the refolding process.

Key words human group IB phospholipase A2 (IB-PLA2); refolding; first disulfide bond; propeptide

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Received: May 13, 2004 Accepted: July 15, 2004

This work was supported by a grant from the National Natural Science Foundation of China (No. 39930060)

*Corresponding author: Tel, 86-21-54921257; Fax, 86-21-54921257; E-mail, [email protected]