Mechanism of soil bacteria (Cupriavidus sp. LA-1) for degrading natural pterin and lumazine pigments.

Diverse microbial metabolic mechanisms help maintain the environmental dynamics of natural compounds in biogeochemical cycles. This study revealed the bacterial mechanism for degrading pterin and lumazine compounds, which are natural cofactors and pigments. The bacterial isolate Cupriavidus sp. LA-1 degraded lumazine via xanthine using a molybdenum-containing lumazine dehydrogenase, an amidohydrolase signature isomerase, and a prenylated flavin mononucleotide-dependent decarboxylase, which are encoded by chromosomal cluster I genes. Among these enzymes, lumazine dehydrogenase is essential for bacterial degradation of lumazine. Cluster I also included a gene encoding a pterin deaminase that converts pterin compounds to their corresponding lumazine forms. The isolate degraded pterin compounds in the organic matter of various insects, reflecting the important effects of lumazine-degrading enzymes and pterin deaminase on the environmental dynamics of natural pterin compounds. The presence of cluster I genes in soil bacteria across phyla suggests that the pterin- and lumazine-degrading mechanism is widely distributed in natural environments. Our results have clarified the degradation of pterin and lumazine compounds in biogeochemical cycles, providing insights into a natural mechanism mediating the degradation of insect pterin and lumazine pigments that had remained undiscovered for many decades.