Senescence marker protein 30 functions as gluconolactonase in L-ascorbic acid biosynthesis, and its knockout mice are prone to scurvy.
We originally identified senescence marker protein 30 (SMP30) as a distinctive protein whose expression decreases in an androgen-independent manner with aging. Here, we report its sequence homology found in two kinds of bacterial gluconolactonases (GNLs) by using the blast search. Then, through a biochemical study, we identify SMP30 as the lactone-hydrolyzing enzyme GNL of animal species. SMP30 purified from the rat liver had lactonase activity toward various aldonolactones, such as d- and l-glucono-delta-lactone, d- and l-gulono-gamma-lactone, and d- and l-galactono-gamma-lactone, with a requirement for Zn(2+) or Mn(2+) as a cofactor. Furthermore, in SMP30 knockout mice, no GNL activity was detectable in the liver. Thus, we conclude that SMP30 is a unique GNL in the liver. The lactonase reaction with l-gulono-gamma-lactone is the penultimate step in l-ascorbic acid (AA) biosynthesis, and the essential role of SMP30 in this synthetic process was verified here by a nutritional study using SMP30 knockout mice. These knockout mice (n = 6), fed a vitamin C-deficient diet, did not thrive; i.e., they displayed symptoms of scurvy such as bone fracture and rachitic rosary and then died by 135 days after the start of receiving the deficient diet. The AA levels in their livers and kidneys at the time of death were <1.6% of those in WT control mice. In addition, by using the SMP30 knockout mouse, we demonstrate that the alternative pathway of AA synthesis involving d-glucurono-gamma-lactone operates in vivo, although its flux is fairly small.
Kondo
Yoshitaka
Y
Department of Molecular Pathology, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015, Japan.
Inai
Yoko
Y
Sato
Yasunori
Y
Handa
Setsuko
S
Kubo
Sachiho
S
Shimokado
Kentaro
K
Goto
Sataro
S
Nishikimi
Morimitsu
M
Maruyama
Naoki
N
Ishigami
Akihito
A
D000375:Aging / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D001205:Ascorbic Acid / Q000096:biosynthesis*; D015415:Biomarkers / Q000378:metabolism; D001835:Body Weight; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D051381:Rats; D012614:Scurvy / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D015238:Sulfotransferases
D015415:Biomarkers; D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C513324:Rgn protein, mouse; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C020579:gluconolactonase; D001205:Ascorbic Acid