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Deyu Xu,Jing Zhao,Guoqiang Cao,Jinyu Wang,Qinggang Li,Ping Zheng,Shuxin Zhao,Jibin Sun 한국생물공학회 2018 Biotechnology and Bioprocess Engineering Vol.23 No.1
Phosphoenolpyruvate carboxylase (PEPC) catalyzes the carboxylation of phosphoenolpyruvate (PEP) in the presence of bicarbonate to form oxaloacetate (OAA), and it plays an important role in high-efficient production of OAA-derived metabolites such as lysine, glutamate and succinate. However, PEPCs often suffered from serious feedback inhibition by various metabolic effectors like aspartate. Here, the feedback inhibition of PEPC from Corynebacterium glutamicum was removed by adding a short terminal peptide like His-tag. The effect of His-tag location on the structure and important properties such as activity, thermostability and feedback inhibition of PEPC has been investigated. The purified untagged PEPC, Nterminal His-tagged PEPC (PEPC-N-His) and C-terminal His-tagged PEPC (PEPC-C-His) were characterized. PEPCN- His (439.71/sec/mM) showed a 1.26 and 186-fold higher catalytic efficiency than untagged PEPC (348.59/sec/mM) and PEPC-C-His (2.36/sec/mM), respectively. Both PEPCN- His and untagged PEPC were significantly inhibited by aspartate at the concentrations above 4 mM (residual activities < 10%), while PEPC-C-His was almost desensitized to aspartate within 10 mM (around 90% of residual activity). Structural analysis showed that the extension of C-terminus may cause steric hindrance for aspartate binding with enzymes, leading to the deregulation of feedback inhibition of PEPC-C-His. This study provides a deeper understanding of the effect of terminal fragments on the structure and function of PEPCs, and helps to engineer the feedback inhibition of PEPCs and structurally similar enzymes.
Improving comparison results on preconditioned generalized accelerated overrelaxation methods
Guangbin Wang,Deyu Sun 한국전산응용수학회 2015 Journal of applied mathematics & informatics Vol.33 No.1
In this paper, we present preconditioned generalized accelerated overrelaxation (GAOR) methods for solving weighted linear least square problems. We compare the spectral radii of the iteration matrices of the preconditioned and the original methods. The comparison results show that the preconditioned GAOR methods converge faster than the GAOR method whenever the GAOR method is convergent. Finally, we give a numerical example to confirm our theoretical results.
IMPROVING COMPARISON RESULTS ON PRECONDITIONED GENERALIZED ACCELERATED OVERRELAXATION METHODS
Wang, Guangbin,Sun, Deyu The Korean Society for Computational and Applied M 2015 Journal of applied mathematics & informatics Vol.33 No.1
In this paper, we present preconditioned generalized accelerated overrelaxation (GAOR) methods for solving weighted linear least square problems. We compare the spectral radii of the iteration matrices of the preconditioned and the original methods. The comparison results show that the preconditioned GAOR methods converge faster than the GAOR method whenever the GAOR method is convergent. Finally, we give a numerical example to confirm our theoretical results.