Distribution of delta-aminolevulinic acid biosynthetic pathways among phototrophic bacterial groups.
Two biosynthetic pathways are known for the universal tetrapyrrole precursor, delta-aminolevulinic acid (ALA). In the ALA synthase pathway which was first described in animal and some bacterial cells, the pyridoxal phosphate-dependent enzyme ALA synthase catalyzes condensation of glycine and succinyl-CoA to form ALA with the loss of C-1 of glycine as CO2. In the five-carbon pathway which was first described in plant and algal cells, the carbon skeleton of glutamate is converted intact to ALA in a proposed reaction sequence that requires three enzymes, tRNA(Glu), ATP, Mg2+, NADPH, and pyridoxal phosphate. We have examined the distribution of the two ALA biosynthetic pathways among various genera, using cell-free extracts obtained from representative organisms. Evidence for the operation of the five-carbon pathway was obtained by the measurement of RNase-sensitive label incorporation from glutamate into ALA, using 3,4-[3H]glutamate or 1-[14C]glutamate as substrate. ALA synthase activity was indicated by RNase-insensitive incorporation of label from 2-[14C]glycine into ALA. The distribution of the two pathways among the bacteria tested was in general agreement with their previously established phylogenetic relationships and clearly indicates that the five-carbon pathway is the more ancient process, whereas the pathway utilizing ALA synthase probably evolved much later. The five-carbon pathway is apparently the more widely utilized one among bacteria, while the ALA synthase pathway seems to be limited to the alpha subgroup of purple bacteria.
Avissar
Y J
YJ
Division of Biology and Medicine, Brown University, Providence, RI 02912.
Ormerod
J G
JG
Beale
S I
SI
D000622:Aminolevulinic Acid / Q000096:biosynthesis*; D001419:Bacteria / Q000378:metabolism*; D002844:Chromatium / Q000378:metabolism; D003901:Desulfovibrio / Q000378:metabolism; D007982:Levulinic Acids / Q000096:biosynthesis*; D012231:Rhizobium / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000378:metabolism; D012246:Rhodospirillum / Q000378:metabolism
D007982:Levulinic Acids; D000622:Aminolevulinic Acid