Plant Molecular Biology 34: 843–854, 1997.
1997 Kluwer Academic Publishers. Printed in Belgium.
Maize glutathione-dependent formaldehyde dehydrogenase cDNA: a novel
plant gene of detoxiﬁcation
and Heinrich Sandermann Jr.
GSF – Forschungszentrum f
ur Umwelt und Gesundheit, Institut f
ur Biochemische Pﬂanzenpathologie, 85764
Oberschleissheim, Germany (
author for correspondence);
present address: Botanisches Institut der Universit
Menzinger Str. 67, 80638 M
Received 26 November 1996; accepted in revised form 28 March 1997
Key words: alcohol dehydrogenase, enzyme evolution, formaldehyde detoxiﬁcation, glutathione-dependentform-
aldehyde dehydrogenase,heterologous expression
We have previously shown that intact plants and cultured plant cells can metabolize and detoxify formaldehyde
through the action of a glutathione-dependent formaldehyde dehydrogenase (FDH), followed by C-1 metabolism
of the initial metabolite (formic acid). The cloning and heterologous expression of a cDNA for the glutathione-
dependent formaldehyde dehydrogenase from Zea mays L. is now described. The functional expression of the
maize cDNA in Escherichia coli proved that the cloned enzyme catalyses the NAD
- and glutathione (GSH)-
dependent oxidation of formaldehyde. The deduced amino acid sequence of 41 kDa was on average 65% identical
with class III alcohol dehydrogenases from animals and less than 60% identical with conventional plant alcohol
dehydrogenases(ADH)utilizing ethanol. Genomic analysissuggested theexistenceof a single gene for this cDNA.
Phylogenetic analysis supports the convergent evolution of ethanol-consuming ADHs in animals and plants from
formaldehyde-detoxifying ancestors. The high structural conservation of present-day glutathione-dependent FDH
in microorganisms, plants and animals is consistent with a universal importance of these detoxifying enzymes.
The detoxiﬁcation of formaldehyde is a general
need of all living cells [15, 17, 49]. The highly
reactive compound is formed in normal metabolism,
but in addition there is the possibility of exposure
to exogenous formaldehyde . There are several
enzyme systems which eliminate formaldehyde .
The most important one is the NAD
- and GSH-
dependent formaldehyde dehydrogenase (FDH, EC
188.8.131.52) . The true substrate for this enzyme was
shown to be S-hydroxymethylglutathione (HMGSH),
which is formed spontaneously from reduced GSH
and formaldehyde [35, 45]. Microbial and animal
GSH-dependent FDHs have been assigned to class
III of the zinc-containing, dimeric, medium-protein-
GenBank and DDBJ Nucleotide Sequence Databases under the
accession number Y11029.
chain-lengthalcohol dehydrogenasefamily (ADH, EC
184.108.40.206) [17, 26, 32]. This family consists of at least
six classes which differ in substrate speciﬁcities, tis-
sue distribution and evolutionary patterns [12, 15, 28,
32]. Class I comprises the ‘classical’ liver ADHs ,
which are of recent origin and have evolved faster than
class III enzymes. Class IIADHs arealso ethanol-
active enzymes present in liver, but are less abundant
than class I ADHs. Class IV is mainly responsible for
the metabolism of ingested ethanol in the stomach,
whereas the tissue distribution and enzymatic function
of classes V and VI are much less deﬁned until now
. Only class III ADH/FDH has also been detected
in cephalopods, insects and nematodes [4, 18, 23, 33].
has been analysed at the DNA level only in yeast and
bacterial species [3, 17, 26, 37, 42, 50].
The medium-chain ADH enzymes represent a sys-
tem of related proteins, which are well classiﬁed in
GR: 201001952, Pips nr. 138318 BIO2KAP
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