Selenium in chemistry and biochemistry in comparison to sulfur.
What makes selenoenzymes--seen from a chemist's view--so special that they cannot be substituted by just more analogous or adapted sulfur proteins? This review compiles and compares physicochemical properties of selenium and sulfur, synthetic routes to selenocysteine (Sec) and its peptides, and comparative studies of relevant thiols and selenols and their (mixed) dichalcogens, required to understand the special role of selenium in selenoproteins on the atomic molecular level. The biochemically most relevant differences are the higher polarizability of Se- and the lower pKa of SeH. The latter has a strikingly different pH-dependence than thiols, with selenols being active at much lower pH. Finally, selected typical enzymatic mechanisms which involve selenocysteine are critically discussed, also in view of the authors' own results.
Wessjohann
Ludger A
LA
Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle/Saale, Germany. wessjohann@ipb-halle.de
Schneider
Alex
A
Abbas
Muhammad
M
Brandt
Wolfgang
W
D000818:Animals; D005560:Formate Dehydrogenases / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D012643:Selenium / Q000737:chemistry* / Q000378:metabolism*; D017279:Selenocysteine / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D051140:Selenoproteins / Q000737:chemistry / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry* / Q000378:metabolism*; D013880:Thioredoxin-Disulfide Reductase / Q000737:chemistry / Q000378:metabolism
D010455:Peptides; D051140:Selenoproteins; D013438:Sulfhydryl Compounds; D017279:Selenocysteine; D013455:Sulfur; D005979:Glutathione Peroxidase; D005560:Formate Dehydrogenases; D013880:Thioredoxin-Disulfide Reductase; D012643:Selenium