Adenosylcobinamide kinase / adenosylcobinamide phosphate guanyltransferase (CobU)
CobU is a bacterial bifunctional cobalbumin biosynthesis enzyme which display adenosylcobinamide kinase and adenosylcobinamide phosphate guanyltransferase activity and is a key participant in the final stages of cobalamin biosynthesis where it is involved in nucleotide loop assembly. CobU is a homotrimer which functions both as a kinase and as a nucleotidyl transferase. It phosphorylates of adenosylcobinamide to form adenosylcobinamide phosphate (using a variety of nucleotides as the phosphate donor) and then adds GMP to adenosylcobinamide phosphate to form adenosylcobinamide-GDP, specifically using GTP.
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