Abstract
Because of the absence of an arylalkylamine N-acetyltransferase (AANAT) homolog in the plant genome, the proposal was made that a GCN5-related N-acetyltransferase superfamily gene (GNAT) could be substituted for AANAT. To clone rice serotonin N-acetyltransferase (SNAT), we expressed 31 rice GNAT cDNAs in Escherichia coli and screened SNAT activity by measuring N-acetyltryptamine after application with 1 mm tryptamine. GNAT5 was shown to produce high levels of N-acetyltryptamine in E. coli, suggesting a possible rice SNAT. To confirm SNAT activity, the GNAT5 protein was purified through affinity purification from E. coli culture. The purified recombinant GNAT5 showed high SNAT enzyme activity catalyzing serotonin into N-acetylserotonin. The values for Km and Vmax were 385 μm and 282 pmol/min/mg protein, respectively. An in vitro enzyme assay of purified SNAT showed N-acetylserotonin formation to be proportional to enzyme concentration and time, with peak activity at pH 8.8. High substrate concentrations above 1 mm serotonin inhibited SNAT activity. Finally, the mRNA level of SNAT was higher in shoots than in roots, but it was expressed constitutively, unlike N-acetylserotonin methyltransferase (ASMT), the terminal enzyme in melatonin synthesis. These results suggest that ASMT rather than SNAT is the rate-limiting enzyme of melatonin biosynthesis in plants.
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Claims 10
Claim · model-written summary
GNAT5 produced high N-acetyltryptamine levels in E. coli.
- Taxon
- rice
Oryza sativat0 - Gene
- GNAT5e0
- Outcome
- high levels of N-acetyltryptaminee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GNAT5 was shown to produce high levels of N-acetyltryptamine in E. coli”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
Purified recombinant GNAT5 showed high SNAT activity converting serotonin to N-acetylserotonin.
- Taxon
- riceOryza sativat0
- Gene
- GNAT5e0
- Outcome
- high SNAT enzyme activity catalyzing serotonin into N-acetylserotonine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“purified recombinant GNAT5 showed high SNAT enzyme activity catalyzing serotonin into N-acetylserotonin”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
SNAT Km was 385 μm.
- Taxon
- riceOryza sativat0
- Gene
- rice serotonin N‐acetyltransferaset0
- Outcome
- Kme0
- Value
- 385 μme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The values for Km and Vmax were 385 μm and 282 pmol/min/mg protein, respectively”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
SNAT Vmax was 282 pmol/min/mg protein.
- Taxon
- riceOryza sativat0
- Gene
- rice serotonin N‐acetyltransferaset0
- Outcome
- Vmaxe0
- Value
- 282 pmol/min/mg proteine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The values for Km and Vmax were 385 μm and 282 pmol/min/mg protein, respectively”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
N-acetylserotonin formation increased with enzyme concentration and time.
- Taxon
- riceOryza sativat0
- Gene
- enzymee0
- Outcome
- N-acetylserotonin formatione0
- Direction
- proportionale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N-acetylserotonin formation to be proportional to enzyme concentration and time”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
SNAT activity peaked at pH 8.8.
- Taxon
- riceOryza sativat0
- Outcome
- activitye0
- Direction
- peake0
- Value
- pH 8.8e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“peak activity at pH 8.8”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
Serotonin concentrations above 1 mm inhibited SNAT activity.
- Taxon
- riceOryza sativat0
- Treatment
- above 1 mm serotonine0
- Outcome
- SNAT activitye0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“High substrate concentrations above 1 mm serotonin inhibited SNAT activity”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
SNAT mRNA was higher in shoots than roots.
- Taxon
- riceOryza sativat0
- Organ / stage
- shootse0
- Gene
- SNATe0
- Outcome
- mRNA level of SNATe0
- Direction
- highere0
- Comparator
- rootse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mRNA level of SNAT was higher in shoots than in roots”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
SNAT was expressed constitutively, unlike ASMT.
- Taxon
- riceOryza sativat0
- Gene
- ASMTe0
- Outcome
- expressed constitutivelye0
- Comparator
- N-acetylserotonin methyltransferase (ASMT)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it was expressed constitutively, unlike N-acetylserotonin methyltransferase (ASMT)”
t0“rice serotonin N‐acetyltransferase”
Claim · model-written summary
Authors infer ASMT, rather than SNAT, limits plant melatonin biosynthesis.
- Taxon
- riceOryza sativat0
- Gene
- ASMTe0
- Outcome
- rate-limiting enzyme of melatonin biosynthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ASMT rather than SNAT is the rate-limiting enzyme of melatonin biosynthesis in plants”
t0“rice serotonin N‐acetyltransferase”
The same questions in other papers
serotonin · molecular: metabolites · Oryza sativa (rice)Results agree
1 paper in the same direction as this paper
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.