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N 5 , N 10 -methylenetetrahydromethanopterin dehydrogenase (H 2 -forming) from the extreme thermophile Methanopyrus kandleri

N 5 , N 10 -methylenetetrahydromethanopterin dehydrogenase (H 2 -forming) from the extreme... 203 156 156 1 1 K. Ma C. Zirngibl D. Linder K. O. Stetter R. K. Thauer Laboratorium für Mikrobiologie, Fachbereich Biologie Philipps-Universität Marburg Karl-von-Frisch-Strasse W-3550 Marburg/Lahn Federal Republic of Germany Fachbereich Humanmedizin, Biochemisches Institut Justus-Liebig-Universität Gießen W-6300 Gießen Federal Republic of Germany Lehrstuhl für Mikrobiologie Universität Regensburg Universitätsstrasse 31 W-8400 Regensburg Federal Republic of Germany Abstract Methanopyrus kandleri is a novel abyssal methanogenic archaebacterium growing at 110°C on H 2 and CO 2 . The N 5 , N 10 -methylenetetrahydromethanopterin dehydrogenase, an enzyme involved in methanogenesis from CO 2 and H 2 , was purified from this hyperthermophile and characterized. The dehydrogenase was found to be composed of only one polypeptide of apparent molecular mass 44 kDa. The UV/Vis spectrum was similar to that of albumin. The protein catalyzed the reversible dehydrogenation of N 5 , N 10 -methylenetetra-hydromethanopterin (CH 2 =H 4 MPT) to N 5 , N 10 -methenyltetrahydromethanopterin (CH = H 4 MPT 4 ) and molecular hydrogen: CH = H 4 MPT 4 + H 2 . The rate of CH 2 =H 4 MPT dehydrogenation (apparent V max ) at 65°C and pH5.8 was 1500 U/mg, the apparent K m for CH 2 =H 4 MPT was 50 μM, the Arrhenius activation energy was 52 kJ/mol, and the Q 10 between 30°C and 70°C was 2.-. The specific activity increased hyperbolically with the proton concentration between pH 7 and pH 4.5. The purified dehydrogenase did not catalyze the reduction of viologen dyes, of coenzyme F 420 , and of pyridine nucleotides with either CH 2 =H 4 MPT or H 2 . For activity the CH 2 =H 4 MPT dehydrogenase required the presence of salts. Fifty percent of maximal activity was reached at salt concentrations of 100 mM, potassium phosphate, potassium chloride, and sodium chloride being almost equally effective in stimulating the enzyme activity. Cell extracts of M. kandleri did not loose CH 2 =H 4 MPT dehydrogenase activity when incubated at 90°C for 60 min. The purified enzyme, however, proved very themolabile. The N-terminal amino acid sequence of the dehydrogenase was determined and compared with that of the CH 2 =H 4 MPT dehydrogenase (H 2 -forming) from Methanobacterium thermoautotrophicum . Significant similarity was found. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Microbiology Springer Journals

N 5 , N 10 -methylenetetrahydromethanopterin dehydrogenase (H 2 -forming) from the extreme thermophile Methanopyrus kandleri

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References (30)

Publisher
Springer Journals
Copyright
Copyright © 1991 by Springer-Verlag
Subject
Life Sciences; Biotechnology; Biochemistry, general; Cell Biology; Ecology; Microbial Ecology; Microbiology
ISSN
0302-8933
eISSN
1432-072X
DOI
10.1007/BF00418186
Publisher site
See Article on Publisher Site

Abstract

203 156 156 1 1 K. Ma C. Zirngibl D. Linder K. O. Stetter R. K. Thauer Laboratorium für Mikrobiologie, Fachbereich Biologie Philipps-Universität Marburg Karl-von-Frisch-Strasse W-3550 Marburg/Lahn Federal Republic of Germany Fachbereich Humanmedizin, Biochemisches Institut Justus-Liebig-Universität Gießen W-6300 Gießen Federal Republic of Germany Lehrstuhl für Mikrobiologie Universität Regensburg Universitätsstrasse 31 W-8400 Regensburg Federal Republic of Germany Abstract Methanopyrus kandleri is a novel abyssal methanogenic archaebacterium growing at 110°C on H 2 and CO 2 . The N 5 , N 10 -methylenetetrahydromethanopterin dehydrogenase, an enzyme involved in methanogenesis from CO 2 and H 2 , was purified from this hyperthermophile and characterized. The dehydrogenase was found to be composed of only one polypeptide of apparent molecular mass 44 kDa. The UV/Vis spectrum was similar to that of albumin. The protein catalyzed the reversible dehydrogenation of N 5 , N 10 -methylenetetra-hydromethanopterin (CH 2 =H 4 MPT) to N 5 , N 10 -methenyltetrahydromethanopterin (CH = H 4 MPT 4 ) and molecular hydrogen: CH = H 4 MPT 4 + H 2 . The rate of CH 2 =H 4 MPT dehydrogenation (apparent V max ) at 65°C and pH5.8 was 1500 U/mg, the apparent K m for CH 2 =H 4 MPT was 50 μM, the Arrhenius activation energy was 52 kJ/mol, and the Q 10 between 30°C and 70°C was 2.-. The specific activity increased hyperbolically with the proton concentration between pH 7 and pH 4.5. The purified dehydrogenase did not catalyze the reduction of viologen dyes, of coenzyme F 420 , and of pyridine nucleotides with either CH 2 =H 4 MPT or H 2 . For activity the CH 2 =H 4 MPT dehydrogenase required the presence of salts. Fifty percent of maximal activity was reached at salt concentrations of 100 mM, potassium phosphate, potassium chloride, and sodium chloride being almost equally effective in stimulating the enzyme activity. Cell extracts of M. kandleri did not loose CH 2 =H 4 MPT dehydrogenase activity when incubated at 90°C for 60 min. The purified enzyme, however, proved very themolabile. The N-terminal amino acid sequence of the dehydrogenase was determined and compared with that of the CH 2 =H 4 MPT dehydrogenase (H 2 -forming) from Methanobacterium thermoautotrophicum . Significant similarity was found.

Journal

Archives of MicrobiologySpringer Journals

Published: Jul 1, 1991

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