title: Evidence for a dimeric structure of rat liver serine dehydratase.
abstract: Rat liver serine dehydratase (SDH) is known to be involved in gluconeogenesis. It has long been believed to be a dimeric protein with the subunit molecular weight (M(r)) of 34,000. Recently, sheep liver SDH was reported to be a monomer with a M(r) of 38,000. The native M(r) of rat SDH was only determined by the ultracentrifugation method more than three decades ago, and that of sheep SDH was done by the method of gel chromatography. The primary to quaternary structures of a given enzyme in a specific mammalian organ are usually conserved among various species. The aim of the present investigation is to clarify the structural differences between rat and sheep SDHs. First, we found that the amino acid composition reported for sheep SDH was statistically similar to that of rat SDH. Second, immunoblot analysis using anti-rat SDH IgG as the probe showed the size of sheep SDH to be a M(r) of 30,500, whereas that of SDH was about M(r) of 35,000. On the other hand, the native size of rat SDH was assessed by two methods: (1) the laser light scattering method demonstrated that rat SDH had a M(r) of 66,800, consistent with the previous value (M(r)=64,000); (2) cross-linking experiments of the purified rat SDH with dimethyl suberimidate revealed the existence of a dimeric form by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The present results clearly confirm that rat SDH is a dimer, and suggest that sheep SDH is similar to rat SDH immunologically, but with a molecular weight 7500 smaller than reported previously.
authors.affiliation: Faculty of Medicine, Department of Biochemistry, Toyama Medical and Pharmaceutical University, Toyama 930-0194, Japan. hogawa@ms.toyama-mpu.ac.jp
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Ogawa
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Gomi
authors.forename: Fusao
authors.initials: F
authors.lastname: Takusagawa
authors.forename: Toru
authors.initials: T
authors.lastname: Masuda
authors.forename: Takuya
authors.initials: T
authors.lastname: Goto
authors.forename: Takanobu
authors.initials: T
authors.lastname: Kan
authors.forename: Num-Ho
authors.initials: NH
authors.lastname: Huh
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D004120:Dimethyl Suberimidate / Q000737:chemistry; D006801:Humans; D012695:L-Serine Dehydratase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D007834:Lasers; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D020836:Protein Structure, Quaternary; D051381:Rats; D017207:Rats, Sprague-Dawley; D012756:Sheep
chemical_list: D000596:Amino Acids; D003432:Cross-Linking Reagents; D004120:Dimethyl Suberimidate; D012695:L-Serine Dehydratase