期刊
FEBS OPEN BIO
卷 7, 期 8, 页码 1126-1143出版社
WILEY
DOI: 10.1002/2211-5463.12249
关键词
enzyme inhibitors; enzyme kinetics; enzyme mutations; enzyme promiscuity; glycolysis metabolism; triosephosphate isomerase
资金
- CSIR-Institute of Microbial Technology (IMTECH), Chandigarh
- Indian Institute of Science Education and Research (IISER), Mohali, India
- Centre of excellence in Frontier Areas of Science and Technology (CoE-FAST), Ministry of Human Resource Development, Govt. of India
The eight-stranded (beta/alpha)(8) barrel fold known as the Triosephosphate isomerase (TIM) barrel is the most commonly observed fold in enzymes, displaying an eightfold structural symmetry. The sequences and structures of different TIM barrel enzymes suggest that nature exploits the modularity inherent in the eightfold symmetry to generate enzymes with diverse enzymatic activities and, in certain cases, more than one catalytic activity per enzyme. Here, we report the discovery, verification, and characterization of such an additional activity, a novel endoglucanase/cellulase activity in what is otherwise a triosephosphate isomerase from the hyperthermophile archaeon Pyrococcus furiosus (PfuTIM). The activity is seen in two different ranges of temperatures, with one maximum at 40 degrees C and a second maximum close to 100 degrees C. The endoglucanase/cellulase activity is inhibited by norharman, a TIM inhibitor, which is suspected to bind at a site different to that of the regular substrate, glyceraldehyde-3-phosphate (G3P). However, endoglucanase/cellulose activity is not inhibited either by G3P analogs or by glycine-scanning mutations involving residues in loops 1, 4, and 6 of PfuTIM, which are known to be important for TIM activity. It appears, therefore, that two different sites on PfuTIM are responsible for the observed TIM and endoglucanase activities. We discuss possible correlations between this discovery and certain unusual features of the glycolytic pathway in P. furiosus.
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