MetaCyc Enzyme: D-galacturonate reductase

Species: Euglena gracilis Z

The apparent molecular mass of the enzyme was determined to be 38 kDa by SDS-PAGE and 39 kDa by gel filtration chromatography, indicating that it is a monomer in its native state [Ishikawa06].

The substrate specificity and the animo-terminal sequence of the enzyme were shown to be distinct from the D-galacturonate reductases from strawberry and mold [Ishikawa06].

Molecular Weight of Polypeptide: 38.0 kD (experimental) [Ishikawa06 ]

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Created 08-Jan-2010 by Fulcher CA , SRI International

Enzymatic reaction of: D-galacturonate reductase

Synonyms: D-galacturonic acid reductase

EC Number:

aldehydo-D-galacturonate + NADPH + H+ <=> aldehydo-L-galactonate + NADP+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

The reaction is irreversible in the direction shown. [Ishikawa06]

Alternative Substrates for aldehydo-D-galacturonate: α-D-xylopyranose [Ishikawa06 ] , D-glucuronate [Ishikawa06 ] , β-L-galactose [Ishikawa06 ] , D-galactose [Ishikawa06 ] , D-glucose [Ishikawa06 ] , L-arabinose [Ishikawa06 ] , DL-glyceraldehyde [Ishikawa06 ]

In Pathways: L-ascorbate biosynthesis V

The reaction product aldehydo-L-galactonate was identified by HPLC. The enzyme could use both NADPH and NADH in a ratio of 10 to 1.8, respectively indicating a preference for NADPH. The enzyme showed a broad substrate specificity, but highest catalytic efficiency for D-galacturonate and D-glucuronate. Neither menadione nor 4-nitrobenzaldehyde could serve as substrates. In vitro the enzyme could not use aldehydo-L-galactonate and NADP+ as substrate in the reverse direction. The enzyme appeared to be activated in the presence of hydrogen peroxide, a compound involved in redox homeostasis in the cell [Ishikawa06].

Kinetic Parameters:

Km (μM)

pH(opt): 7.2 [Ishikawa06]


Ishikawa06: Ishikawa T, Masumoto I, Iwasa N, Nishikawa H, Sawa Y, Shibata H, Nakamura A, Yabuta Y, Shigeoka S (2006). "Functional characterization of D-galacturonic acid reductase, a key enzyme of the ascorbate biosynthesis pathway, from Euglena gracilis." Biosci Biotechnol Biochem 70(11);2720-6. PMID: 17090924

Richard09: Richard P, Hilditch S (2009). "D-galacturonic acid catabolism in microorganisms and its biotechnological relevance." Appl Microbiol Biotechnol 82(4);597-604. PMID: 19159926

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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