Ribonucleotide reductase manganese-containing

Recently, a new type of ribonucleotide reductase that did not require coenzyme-B12 or iron for activity was discovered in the coryneform bacteria Brevibacteriium ammoniagenes and Micrococcus luteus (228) this enzyme requires manganese instead. Like the diiron-containing enzyme from E. coli, the enzyme from B. ammoniagenes consists of two components, a 30 kDa B1 subunit that binds the nucleotides and 100 kDa B2 subunit consisting of two 50-kDa chains with at least one Mn per chain... 

Enzyme from Mn-deficient cells showed no ribonucleotide reductase activity but could be activated by addition of Mn (215). Furthermore, Mn was incorporated into the B2 subunit when the bacteria were grown on MnCL-enriched medium (8). These experiments strongly implicate a manganese containing active site. 

The distribution of iron-dependent ribonucleotide reductase among other bacteria cannot be assessed at present. Unlike cobalt or manganese, iron deficiency in growth media would lead to various biochemical lesions difficult to distinguish from each other. No other bacterial enzymes have become known that contain non-heme-iron like the E. coli protein. However we shall return to Fe-ribonucleotide reductases in the viral and eukaryotic enzyme systems. 

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