ORF7 from Amycolatopsis orientalis catalyzes decarboxylation of Nδ-methylarginine and amine oxidation of arginine: Biosynthetic implications.
A key step in the biosynthesis of the polyene polyketide ECO-0501 by Amycolatopsis orientalis ATCC 43491 is thought to involve oxidative decarboxylation of arginine or Nδ-methylarginine to the corresponding primary amide. This reaction is the centerpiece of a recently identified biosynthetic cassette that generates 4-guanidinobutyryl thioesters to serve as starter units for polyketide synthesis. We examined the reaction of ORF7, the predicted ECO-0501 biosynthetic decarboxylase, with arginine, and saw no evidence of decarboxylation. Instead, we observed exclusive amine oxidation to generate 2-oxoarginine, with a kcat/KM,Argof 5.6×106M-1s-1, typical of values measured for physiological amino acid decarboxylases. In contrast, when ORF7 was incubated with Nδ-methylarginine, we observed exclusive decarboxylation to generate 4-(N1-methylguanidino)butyramide. These differing reactive pathways provide insight into the biosyntheses of guanidinobutyryl-derived polyketides and demonstrate the biosynthetic versatility of arginine-processing decarboxylases. In addition, it suggests that ORF7 may be an incisive model system for dissecting the determinants of flavoprotein-catalyzed oxidase and monooxygenase modes of reactivity.
Department of Chemistry, Carleton College, 1 North College Street, Northfield, MN 55057, USA.
Natalie L
NL
Kingston
Department of Chemistry, Carleton College, 1 North College Street, Northfield, MN 55057, USA.
Yun
Y
Liu
Department of Chemistry, Carleton College, 1 North College Street, Northfield, MN 55057, USA. Electronic address: ccalderone@carleton.edu.
Christopher T
CT
Calderone
D039903:Actinobacteria / Q000201:enzymology*; D000577:Amides / Q000378:metabolism; D001120:Arginine / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D055162:Biocatalysis; D002262:Carboxy-Lyases / Q000378:metabolism*; D003653:Decarboxylation; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D006146:Guanidines; D008958:Models, Molecular; D010084:Oxidation-Reduction; D019323:omega-N-Methylarginine / Q000378:metabolism
C515838:13-hydroxy-2,12,14,16,22-pentamethyl-28-(N-methyl-guanidino)-octacosa-2,4,6,8,10,14,20,24-octaenoic acid (2-hydroxy-5-oxo-cyclopent-1-enyl)-amide; D000577:Amides; D001426:Bacterial Proteins; D005231:Fatty Acids, Unsaturated; D006146:Guanidines; D019323:omega-N-Methylarginine; D001120:Arginine; D002262:Carboxy-Lyases
Biosynthesis; Flavoenzyme; Monoxygenase