PQQ-dependent methanol dehydrogenases: rare-earth elements make a difference

• Published in: Applied microbiology and biotechnology Vol. 98; no. 14; pp. 6163 - 6183
• Main Authors: Keltjens, Jan T, Pol, Arjan, Reimann, Joachim, Op den Camp, Huub J. M
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.07.2014; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Alcohol; Alcohol Oxidoreductases; Alcohol Oxidoreductases - chemistry; Alcohol Oxidoreductases - genetics; Alcohol Oxidoreductases - metabolism; aldehyde dehydrogenase; Amino acids; Analysis; Bacteria; Biomedical and Life Sciences; Biotechnology; Calcium; Calcium - metabolism; Carbon; Catalysis; catalytic activity; Chemicals; chemistry; Coenzymes; Coenzymes - metabolism; Dehydrogenases; Enzymes; enzymology; formaldehyde; Genes; Genetic aspects; genetics; genome; Genomes; genomics; Gram-negative bacteria; Gram-Negative Bacteria - enzymology; Gram-Negative Bacteria - genetics; Gram-positive bacteria; Life Sciences; metabolism; methane; Methane - metabolism; Methanol; Methanol - metabolism; Methanotrophs; Microbial Genetics and Genomics; Microbiology; Microorganisms; Mini-Review; Models, Molecular; Oxidation; Oxidoreductases; Phylogeny; Physiological aspects; PQQ Cofactor; PQQ Cofactor - metabolism; Production processes; Protein Conformation; protein subunits; Protein Subunits - metabolism; Proteins; Rare earth elements; Respiration; sequence analysis; Studies; Trace elements; Netherlands; Methanol dehydrogenase; Pyrroloquinoline quinone; Methanotrophy; Alcohol dehydrogenase; Rare-earth elements; Methylotrophy
• ISSN: 0175-7598; 1432-0614; 1432-0614
• DOI: 10.1007/s00253-014-5766-8

Methanol dehydrogenase (MDH) catalyzes the first step in methanol use by methylotrophic bacteria and the second step in methane conversion by methanotrophs. Gram-negative bacteria possess an MDH with pyrroloquinoline quinone (PQQ) as its catalytic center. This MDH belongs to the broad class of eight-bladed β propeller quinoproteins, which comprise a range of other alcohol and aldehyde dehydrogenases. A well-investigated MDH is the heterotetrameric MxaFI-MDH, which is composed of two large catalytic subunits (MxaF) and two small subunits (MxaI). MxaFI-MDHs bind calcium as a cofactor that assists PQQ in catalysis. Genomic analyses indicated the existence of another MDH distantly related to the MxaFI-MDHs. Recently, several of these so-called XoxF-MDHs have been isolated. XoxF-MDHs described thus far are homodimeric proteins lacking the small subunit and possess a rare-earth element (REE) instead of calcium. The presence of such REE may confer XoxF-MDHs a superior catalytic efficiency. Moreover, XoxF-MDHs are able to oxidize methanol to formate, rather than to formaldehyde as MxaFI-MDHs do. While structures of MxaFI- and XoxF-MDH are conserved, also regarding the binding of PQQ, the accommodation of a REE requires the presence of a specific aspartate residue near the catalytic site. XoxF-MDHs containing such REE-binding motif are abundantly present in genomes of methylotrophic and methanotrophic microorganisms and also in organisms that hitherto are not known for such lifestyle. Moreover, sequence analyses suggest that XoxF-MDHs represent only a small part of putative REE-containing quinoproteins, together covering an unexploited potential of metabolic functions.