Formaldehyde activating enzyme (Fae) and hexulose-6-phosphate synthase (Hps) in <Emphasis Type="Italic">Methanosarcina barkeri</Emphasis>: a possible function in ribose-5-phosphate biosynthesis |
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Authors: | Meike?Goenrich Email author" target="_blank">Rudolf?K?ThauerEmail author Hiroya?Yurimoto Nobuo?Kato |
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Institution: | (1) Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, 35043 Marburg, Germany;(2) Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan |
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Abstract: | Formaldehyde activating enzyme (Fae) was first discovered in methylotrophic bacteria, where it is involved in the oxidation
of methanol to CO2 and in formaldehyde detoxification. The 18 kDa protein catalyzes the condensation of formaldehyde with tetrahydromethanopterin
(H4MPT) to methylene-H4MPT. We describe here that Fae is also present and functional in the methanogenic archaeon Methanosarcina barkeri. The faeA homologue in the genome of M. barkeri was heterologously expressed in Escherichia coli and the overproduced purified protein shown to actively catalyze the condensation reaction: apparent V
max=13 U/mg protein (1 U=μmol/min); apparent Km for H4MPT=30 μM; apparent Km for formaldehyde=0.1 mM. By Western blot analysis the concentration of Fae in cell extracts of M. barkeri was determined to be in the order of 0.1% of the soluble cell proteins. Besides the faeA gene the genome of M. barkeri harbors a second gene, faeB-hpsB, which is shown to code for a 42 kDa protein with both Fae activity (3.6 U/mg) and hexulose-6-phosphate synthase (Hps) activity
(4.4 U/mg). The results support the recent proposal that in methanogenic archaea Fae and Hps could have a function in ribose
phosphate synthesis. |
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Keywords: | Methanogenic archaea Methanosarcina mazei C1-metabolism Ribulose monophosphate pathway Methanogenesis from formaldehyde |
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