Improvingthecatalytic properties and stability of immobilized γ-glutamyltranspeptidase by post-immobilization with Pharmalyte
MT 8-10.5.
Int J Biol Macromol 2017;
105:1581-1586. [PMID:
28414108 DOI:
10.1016/j.ijbiomac.2017.04.050]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 03/22/2017] [Accepted: 04/11/2017] [Indexed: 11/20/2022]
Abstract
γ-Glutamyltranspeptidase (GGT) is a dimeric protein that specifically catalyzes the transfer of γ-glutamyl in the optimum pH range of 8.5-9.0, but has poor in vitro stability under the alkaline conditions. In the present work, GGT was immobilized on a mesoporoustitania oxide whisker (MTWs) carrier to afford MTWs-GGT that was further modified with PharmalyteMT (Phar) 8.0-10.5 to yield MTWs-GGT-Phar. Phar absorbed on MTWs-GGT to form a buffering layer with an isoelectric point of ∼9.2 that isolated the immobilized enzyme from the liquid bulk and significantly in proved the pH tolerance and stability of the immobilized GGT. The MTWs-GGT-Phar exhibited a stable enzyme activity in the pH range of 6.0-11.0 and an optimum temperature 10°C higher than GGT. Its pH stability at pH 11.0 and thermal stability at 50°C were respectively 23.7 times and 19.4 times higher than those of GGT. In addition, the affinity constant of MTWs-GGT-Phar towards GpNA (Km) was 0.597mM, slightly lower than that of free GGT, indicating that Phar had a protective effect on the structure of GGT.
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