Metabolism of 2‐oxoaldehyde in mold

Abstract

Two kinds of methylglyoxal reductases were purified to apparent homogeneity from Aspergillus niger and designated MGR I and MGR II. Both enzymes consisted of a single polypeptide chain with a relative molecular mass of 36000 (MGR I) and 38000 (MGR II). NADPH was specifically required for the activities of both enzymes and Km values for NADPH were 54 μM (MGR I) and 6.8 μM (MGR II). MGR I was specific to 2‐oxoaldehydes [glyoxal, methylglyoxal (Km=15.4 mM) and phenylglyoxal], whereas MGR II was active on both 2‐oxoaldehydes [glyoxal (Km= 10mM), methylglyoxal (Km= 1.43 mM), phenylglyoxal (Km=4.35 mM) and 4,5‐dioxovalerate] and some aldehydes (propionaldehyde and acetaldehyde). Optimal pH values for MGR I and MGR II activities were 9.0 and 6.5 respectively. Both enzymes were inactivated by a brief incubation with 2‐oxoaldehydes (glyoxal, methylglyoxal and phenylglyoxal) in the absence of NADPH. MGR I activity was competitively inhibited by NADP+ and the Ki value for NADP+ was calculated to be 0.49 mM. On the other hand, the inhibition of MGR II activity by NADP+ was of mixed type, the Ki value for NADP+ being 45 μM. MGR I was different from MGR II in amino acid composition.

Identification of Lactaldehyde Dehydrogenase in Methanocaldococcus jannaschii and Its Involvement in Production of Lactate for F 420 Biosynthesis

“…Consequently, the kinetic parameters do not reflect the possible stereospecificity of the enzyme. Unlike the lactaldehyde dehydrogenase purified from Saccharomyces cerevisiae (26,27,39), M. jannaschii lactaldehyde dehydrogenase showed relatively broad substrate specificity and was able to use a variety of aldehyde substrates. M. jannaschii lactaldehyde dehydrogenase was found to utilize DL-glyceraldehyde and crotonaldehyde as substrates, albeit with lower levels of activity than observed with lactaldehyde, and exhibited even less activity with glycolaldehyde, acetaldehyde, acrolein, and formaldehyde (Table 2).…”

“…In addition, a methylglyoxal synthase has been detected in halophilic archaea (42). Methylglyoxal has been shown to be toxic to cells and has been proposed to be involved in the regulation of cellular division (26,39). The methylglyoxal pathway is involved in the detoxification of methylglyoxal generated from dihydroxyacetone phosphate or the catabolism of threonine (40) and results in the formation of lactate from lactaldehyde (27).…”

NMR Characterization of3,6-Dioxa-8-azabicyclo[3.2.1]octanes andN-[Tris(hydroxymethyl)methyl]alanine Formedfrom Methylglyoxal in Tris Buffer Solutions

“…Evaluation of enzyme inactivation observed for 2-oxoaldehydes should therefore take into consideration the bu †er which has been used for the assay as well as the recognized importance of order of addition. 40 The role of aminoalcohols in facilitating 2-oxoaldehyde dehydrogenase activity remains unclear but it is evident that the observation of optimal activity in Tris bu †er41 at pH 8.0 is not due to polymerization or failure of methylglyoxal to react with Tris in neutral solutions.…”

Biochemistry of the Nickel‐Dependent Glyoxalase I Enzymes

“…NADPH-dependent oxidoreductases that catalyze conversion of MG to acetol or lactaldehyde have been identifi ed in E. coli, S. cerevisiae, and several mammalian species. MG conversion to lactaldehyde by MG reductases has been characterized in S. cerevisiae and Aspergillus niger and has also been identifi ed in mammalian liver homogenates [39][40][41]. Additionally aldose reductase enzymes have been characterized as another route of MG catabolism [30,42].…”