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 ]
Enzymatic reaction of: D-galacturonate reductase
Synonyms: D-galacturonic acid reductase
EC Number: 188.8.131.525aldehydo-D-galacturonate + NADPH + H+ → aldehydo-L-galactonate + NADP+
The direction shown, i.e. which substrates are on the left and right sides, 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].
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
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