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Journal of Bacteriology, June 2007, p. 4053-4061, Vol. 189, No. 11
0021-9193/07/$08.00+0     doi:10.1128/JB.01875-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

In Vitro Biosynthesis of Ether-Type Glycolipids in the Methanoarchaeon Methanothermobacter thermautotrophicus{triangledown}

Hiroyuki Morii,1* Tadashi Eguchi,2 and Yosuke Koga1

Department of Chemistry, School of Medicine, University of Occupational and Environmental Health, Yahatanishi-ku, Kitakyushu 807-8555,1 Department of Chemistry and Materials Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan2

Received 13 December 2006/ Accepted 25 March 2007

The biosynthesis of archaeal ether-type glycolipids was investigated in vitro using Methanothermobacter thermautotrophicus cell-free homogenates. The sole sugar moiety of glycolipids and phosphoglycolipids of the organism is the ß-D-glucosyl-(1->6)-D-glucosyl (gentiobiosyl) unit. The enzyme activities of archaeol:UDP-glucose ß-glucosyltransferase (monoglucosylarchaeol [MGA] synthase) and MGA:UDP-glucose ß-1,6-glucosyltransferase (diglucosylarchaeol [DGA] synthase) were found in the methanoarchaeon. The synthesis of DGA is probably a two-step glucosylation: (i) archaeol + UDP-glucose -> MGA + UDP, and (ii) MGA + UDP-glucose -> DGA + UDP. Both enzymes required the addition of K+ ions and archaetidylinositol for their activities. DGA synthase was stimulated by 10 mM MgCl2, in contrast to MGA synthase, which did not require Mg2+. It was likely that the activities of MGA synthesis and DGA synthesis were carried out by different proteins because of the Mg2+ requirement and their cellular localization. MGA synthase and DGA synthase can be distinguished in cell extracts greatly enriched for each activity by demonstrating the differing Mg2+ requirements of each enzyme. MGA synthase preferred a lipid substrate with the sn-2,3 stereostructure of the glycerol backbone on which two saturated isoprenoid chains are bound at the sn-2 and sn-3 positions. A lipid substrate with unsaturated isoprenoid chains or sn-1,2-dialkylglycerol configuration exhibited low activity. Tetraether-type caldarchaetidylinositol was also actively glucosylated by the homogenates to form monoglucosyl caldarchaetidylinositol and a small amount of diglucosyl caldarchaetidylinositol. The addition of Mg2+ increased the formation of diglucosyl caldarchaetidylinositol. This suggested that the same enzyme set synthesized the sole sugar moiety of diether-type glycolipids and tetraether-type phosphoglycolipids.

* Corresponding author. Mailing address: Department of Chemistry, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan. Phone: 81-93-603-1611. Fax: 81-93-693-9921. E-mail: h-morii{at}health.uoeh-u.ac.jp

{triangledown} Published ahead of print on 6 April 2007.

Journal of Bacteriology, June 2007, p. 4053-4061, Vol. 189, No. 11
0021-9193/07/$08.00+0     doi:10.1128/JB.01875-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Morii, H., Kiyonari, S., Ishino, Y., Koga, Y. (2009). A Novel Biosynthetic Pathway of Archaetidyl-myo-inositol via Archaetidyl-myo-inositol Phosphate from CDP-archaeol and D-Glucose 6-Phosphate in Methanoarchaeon Methanothermobacter thermautotrophicus Cells. J. Biol. Chem. 284: 30766-30774 [Abstract] [Full Text]  


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