Reference "Characterization and metabolic function of a peroxisomal sarcosine and pipecolate oxidase from Arabidopsis"

Reference ID

54967

Title

Characterization and metabolic function of a peroxisomal sarcosine and pipecolate oxidase from Arabidopsis

Source

J Biol Chem, 2004, vol. 279, pp. 16947-16953

Authors (7)

Goyer-A	Johnson-T-L
Olsen-L-J	Collakova-E
Shachar-Hill-Y	Rhodes-D
Hanson-A-D

Abstract

Sarcosine oxidase (SOX) is known as a peroxisomal enzyme in mammals and as a sarcosine-
inducible enzyme in soil bacteria. Its presence in plants was unsuspected until
the Arabidopsis genome was found to encode a protein (AtSOX) with approximately
33% sequence identity to mammalian and bacterial SOXs. When overexpressed in
Escherichia coli, AtSOX enhanced growth on sarcosine as sole nitrogen source,
showing that it has SOX activity in vivo, and the recombinant protein catalyzed
the oxidation of sarcosine to glycine, formaldehyde, and H(2) O(2) in vitro.
AtSOX also attacked other N-methyl amino acids and, like mammalian SOXs,
catalyzed the oxidation of l-pipecolate to Delta(1)-piperideine-6-carboxylate.
Like bacterial monomeric SOXs, AtSOX was active as a monomer, contained FAD
covalently bound to a cysteine residue near the C terminus, and was not
stimulated by tetrahydrofolate. Although AtSOX lacks a typical peroxisome-
targeting signal, in vitro assays established that it is imported into
peroxisomes. Quantitation of mRNA showed that AtSOX is expressed at a low level
throughout the plant and is not sarcosine-inducible. Consistent with a low level
of AtSOX expression, Arabidopsis plantlets slowly metabolized supplied
[(14)C]sarcosine to glycine and serine. Gas chromatography-mass spectrometry
analysis revealed low levels of pipecolate but almost no sarcosine in wild type
Arabidopsis and showed that pipecolate but not sarcosine accumulated 6-fold when
AtSOX expression was suppressed by RNA interference. Moreover, the pipecolate
catabolite alpha-aminoadipate decreased 30-fold in RNA interference plants.
These data indicate that pipecolate is the endogenous substrate for SOX in
plants and that plants can utilize exogenous sarcosine opportunistically,
sarcosine being a common soil metabolite.