首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Synthesis of the mannosyl-O-serine (threonine) linkage of glycoproteins from polyisoprenylphosphate mannose in yeast (Hansenula holstii)
Authors:RK Bretthauer  S Wu
Institution:Department of Chemistry, Biochemistry and Biophysics Program, University of Notre Dame, Notre Dame, Indiana 46556 USA
Abstract:The mannolipid synthesized from GDP-mannose and lipid acceptors in a particulate enzyme preparation from the yeast Hansenula holstii (R. K. Bretthauer, S. Wu, and W. E. Irwin, (1973) Biochim. Biophys. Acta, 304, 736–747) has the properties of dolicholmonophosphate mannose. Transfer of 14C]mannose from exogenously supplied, purified mannolipid to endogenous protein acceptors of the particulate enzyme fraction has now been demonstrated. The synthesis of radioactive products which are insoluble in chloroform-methanol and water is dependent upon time and concentrations of substrate, particulate fraction protein, and detergent. Addition of MgCl2 or MnCl2 to incubation mixtures prepared in the absence of these ions had only small stimulatory effects (20–25%), suggesting that the reaction is not dependent upon metal ions. Relatively high concentrations (0.005 m-0.05 m) of EDTA did partially inhibit the reaction, but this is considered to be due to secondary effects.Seventy percent of the radioactivity in the chloroform-methanol insoluble residue was solubilized with hot, neutral citrate buffer. The Chromatographic properties of this material on Sephadex gels and on DEAE-Sephadex were very similar to the properties of glycoprotein products derived from GDP-14C]mannose. The chloroform-methanol insoluble products were also solubilized with Pronase which subsequently resulted in the isolation of a radioactive glycopeptide that contained 25% of the radioactivity transferred from mannolipid. The radioactive component of this glycopeptide was shown by β-elmination experiments and by amino acid analyses to be 14C]mannose residues linked O-glycosidically to serine and threonine residues. It was concluded, therefore, that one function of the mannolipid is to serve as mannosyl donor in the synthesis of the mannosyl-O-serine (threonine) linkage region of glycoproteins which may be part of the cell wall mannan-protein complex. Other mannose-containing products may also be synthesized from the mannolipid, as β-elimination of the chloroform-methanol insoluble fraction or of the Pronase soluble fraction did not result in recovery of all of the radioactivity as 14C]mannose.
Keywords:To whom correspondence should be addressed  
本文献已被 ScienceDirect 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号