B12 Coenzyme-dependent Ribonucleotide Reductase in Rhizobium Species and the Effects of Cobalt Deficiency on the Activity of the Enzyme1
AUTOR(ES)
Cowles, Joe R.
RESUMO
This investigation revealed that the ribonucleotide reductases in extracts of Rhizobium leguminosarum, R. trifolii, R. phaseoli, R. japonicum, and R. meliloti 3DOal (ineffective in nitrogen fixation) are dependent upon B12 coenzyme for activity. Rhizobium and certain Lactobacillus species are the only two groups of organisms known to contain B12 coenzyme-dependent ribonucleotide reductases. Extracts of cobalt-deficient R. meliloti cells assayed in the presence of optimum B12 coenzyme showed a 5- to 10-fold greater ribonucleotide reductase activity than comparable extracts from cells grown on a complete medium. Furthermore, cobalt-deficient cells were abnormally elongated and contained reduced contents of deoxyribonucleic acid. The addition of purified deoxyribonucleosides to cobalt-deficient cultures of R. meliloti failed to alleviate deficiency symptoms.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=249869Documentos Relacionados
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