Biochemical Analysis on the Parallel Pathways of Methionine Biosynthesis in Corynebacterium glutamicum : Biochemical Analysis on the Parallel Pathways of Methionine Biosynthesisin Corynebacterium glutamicum
Biochemical Analysis on the Parallel Pathways of Methionine Biosynthesisin Corynebacterium glutamicum
- 주제(키워드) Corynebacterium glutamicum , cystathionineγ-synthase , metB , methionine , metY , O-acetylhomoserinesulfhydrylasemethionine have been studied extensively in Escherichia coliand Salmonella typhimurium. Although current knowledgeregarding methionine biosyn
- 발행기관 한국미생물·생명공학회
- 발행년도 2007
- 총서유형 Journal
- UCI G704-000169.2007.17.6.016
- KCI ID ART001066443
- 본문언어 영어
초록/요약
Two alternative pathways for methionine biosynthesisare known in Corynebacterium glutamicum: one involvingtransulfuration (mediated by metB and metC) and the otherinvolving direct sulfhydrylation (mediated by metY). In this study,MetB (cystathionine γ-synthase) and MetY (O-acetylhomoserinesulfhydrylase) from C. glutamicum were purified to homogeneityand the biochemical parameters were compared to assess thefunctional and evolutionary importance of each pathway. Themolecular mases of the native MetB and MetY proteins weremeasured to be aproximately 170 and 280 kDa, respectively,showing that MetB was a homotetramer of 40-kDa subunitsand MetY was a homohexamer of 45-kDa subunits. The Kmvalues for the Oand MetY were 3.9 and 6.4 mM, and the maximum catalysisrates were 7.4 (kcat=21 s-1) and 6.0 (kcat=28 s-1) mol mg-1min-1, respectively. This sugests that both MetB and MetYcan be comparably active in vivo. Nevertheles, the Kmvalue for sulfide ions by MetY was 8.6 mM, which wastoo high, considering the physiological condition. Moreover,MetB was active at a broad range of temperatures (30 and65oC) and pH (6.5 and 10.0), as compared with MetY, whichwas active in a range from 30 to 45oC and at pH values from7.0 to 8.5. In addition, MetY was inhibited by methionine,but MetB was not. These biochemical data may provideinsight on the role of the parallel pathways of methioninebiosynthesis in C. glutamicum with regard to cel physiologyand evolution.
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