L-gulono-γ-lactone oxidase expression and vitamin C synthesis in the brain and kidney of the African lungfish, Protopterus annectens.
This study aimed to test the hypothesis that the brain of Protopterus annectens expressed L-gulono-γ-lactone oxidase (gulo/Gulo), the enzyme catalyzing the last step of ascorbate biosynthesis, and could maintain high concentrations of ascorbate during estivation. We cloned and sequenced gulo from the kidney of P. annectens and performed quantitative PCR to determine its mRNA expression in kidney and brain. Gulo activity was assayed and its protein abundance was determined by Western blot using custom-made anti-Gulo antibody. Effects of estivation on concentrations of ascorbate and dehydroascorbate in the kidney and brain were also determined. Both brain and kidney, but not liver, of P. annectens expressed gulo/Gulo. Desiccation induced P. annectens to estivate, and 6 mo of estivation led to drastic decreases in gulo/Gulo expression and ascorbate concentration in the kidney. However, high concentrations of ascorbate and ascorbate + dehydroascorbate were maintained in the brain during estivation, probably resulting from in situ ascorbate synthesis. Control fish were placed in freshwater, where they were fully active in a favorable environment unlike estivation on land. The ability to synthesize ascorbate to ameliorate oxidative stress directly in the brain might contribute to the ability of P. annectens to undergo prolonged estivation on land.
Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore; and.
Biyun
B
Ching
Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore; and.
Jasmine L Y
JL
Ong
Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore; and.
You Rong
YR
Chng
Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore; and.
Xiu Ling
XL
Chen
Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore; and.
Wai P
WP
Wong
Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Republic of Singapore.
Shit F
SF
Chew
Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore; and dbsipyk@nus.edu.sg.
Yuen K
YK
Ip
D000595:Amino Acid Sequence; D000818:Animals; D001205:Ascorbic Acid / Q000096:biosynthesis*; D001834:Body Water; D001921:Brain / Q000201:enzymology*; D017124:Conserved Sequence; D004956:Estivation / Q000502:physiology*; D005399:Fishes / Q000502:physiology*; D007668:Kidney / Q000201:enzymology*; D050544:L-Gulonolactone Oxidase / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D009928:Organ Specificity; D018384:Oxidative Stress; D010802:Phylogeny; D012333:RNA, Messenger / Q000096:biosynthesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D012333:RNA, Messenger; D050544:L-Gulonolactone Oxidase; D001205:Ascorbic Acid
GULO; ascorbate; dehydroascorbate; estivation; oxidative stress