期刊
APPLIED MICROBIOLOGY AND BIOTECHNOLOGY
卷 100, 期 2, 页码 649-659出版社
SPRINGER
DOI: 10.1007/s00253-015-6995-1
关键词
Ketoglutarate dehydrogenase complex; Non-conventional yeast; Organic acids; Site-directed mutagenesis
资金
- National Natural Science Foundation of China [31130043, 21276109]
- National Excellent Doctoral Dissertation of PR China (FANEDD) [201256]
- Program for New Century Excellent Talents in University [NCET-12-0876]
- Fundamental Research Funds for the Central Universities [JUSRP51307A]
- 111 Project [111-2-06]
alpha-Ketoglutarate (alpha-KG) is an important intermediate in the tricarboxylic acid cycle and has broad applications. The mitochondrial ketoglutarate dehydrogenase (KGDH) complex catalyzes the oxidation of alpha-KG to succinyl-CoA. Disruption of KGDH, which may enhance the accumulation of alpha-KG theoretically, was found to be lethal to obligate aerobic cells. In this study, individual overexpression of dihydrolipoamide succinyltransferase (DLST), which serves as the inner core of KGDH, decreased overall activity of the enzyme complex. Furthermore, two conserved active site residues of DLST, His419, and Asp423 were identified. In order to determine whether these residues are engaged in enzyme reaction or not, these two conserved residues were individually mutated. Analysis of the kinetic parameters of the enzyme variants provided evidence that the catalytic reaction of DLST depended on residues His419 and Asp423. Overexpression of mutated DLST not only impaired balanced assembly of KGDH, but also disrupted the catalytic integrity of the enzyme complex. Replacement of the Asp423 residue by glutamate increased extracellular alpha-KG by 40 % to 50 g L-1 in mutant strain. These observations uncovered catalytic roles of two conserved active site residues of DLST and provided clues for effective metabolic strategies for rational carbon flux control for the enhanced production of alpha-KG and related bioproducts.
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