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Methanol dehydrogenase of Methylomonas J: purification, crystallization, and some properties
Abstract:
A methanol dehydrogenase [EC 1.1.99.8] was purified and crystallized from methanol-grown Methylomonas J (formerly Pseudomonas sp. J), an obligate methylotroph. Its molecular weight was estimated to be 135,000 by gel chromatography. The sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis revealed two bands and their molecular weights were approximately 60,000 and 10,000. The enzyme was relatively stable at pH 6 and 10, and was unstable at pH 8. The enzyme activity was lost at pH 4.0; however, the prosthetic group was not liberated from the enzyme. Its isoelectric point was pH 9.3. The visible-ultraviolet absorption, fluorescence, CD, and ESR spectra were measured. The amino acid composition was analyzed after separation of the two components. Primary alcohols and formaldehyde served as substrates. Phenazine methosulfate (PMS) was an effective electron acceptor of the enzyme in the presence of either NH4Cl or methylamine. The enzyme was inhibited partially by metal chelators and completely by Mn2+ and Co2+.
Insights
Researchers purified and crystallized methanol dehydrogenase from Methylomonas J. This study details its molecular weight, subunit composition, stability, spectral properties, and substrate specificity, providing key insights into methylotrophic enzymes.
Area of Science:
- Biochemistry
- Enzymology
- Microbiology
Background:
- Methanol dehydrogenase (MDH) is crucial for methylotrophic bacteria.
- Understanding MDH structure and function aids in metabolic engineering and biocatalysis.
Purpose of the Study:
- To purify and crystallize MDH from Methylomonas J.
- To characterize the enzyme's physicochemical and biochemical properties.
Main Methods:
- Enzyme purification and crystallization.
- Gel chromatography and SDS-PAGE for molecular weight determination.
- Spectroscopic analysis (UV-Vis, fluorescence, CD, ESR).
- Amino acid composition analysis.
- Enzyme activity assays with various substrates and electron acceptors.
Main Results:
- Purified MDH has a molecular weight of 135,000 Da, with subunits of 60,000 and 10,000 Da.
- The enzyme exhibits stability at pH 6 and 10, but is unstable at pH 8 and loses activity at pH 4.0.
- Spectroscopic and amino acid analyses were performed; PMS is an effective electron acceptor.
- MDH is inhibited by metal chelators, Mn2+, and Co2+.
Conclusions:
- The study provides a comprehensive characterization of MDH from Methylomonas J.
- The findings contribute to the understanding of enzyme structure-function relationships in methylotrophs.