Microbial transformation of ent-kaurenoic acid and its 15-hydroxy derivatives by the SG138 mutant of Gibberella fujikuroi.
Feeding experiments with ent-kaurenoic acid (4), 15 alpha-hydroxy-ent-kaurenoic acid (5), 15 beta-hydroxy-ent-kaurenoic acid (6), and mixtures of 4 plus 5 and 4 plus 6 were conducted using the SG138 mutant of Gibberella fujikuroi, to gain information about the phenotype of this unique strain. The biotransformation of 5 gave 7 beta,15 alpha-dihydroxykaurenolide (9) and 7 beta,15 alpha-dihydroxy-ent-kaurenoic acid (13). The incubation of 6 produced 7 beta,15 beta-dihydroxy-ent-kaurenoic acid (7) and 7 beta,15 beta-dihydroxykaurenolide (10). No 15-hydroxylated gibberellins were detected in any of these experiments. The results indicated that a hydroxy group at C-15 does not inhibit 7 beta-hydroxylase activity but in the SG138 strain obstructs the enzymatic ring-B contraction of ent-kaurenoids to gibberellins. Exogenous 4 stimulated both the excretion of ent-kaurene and the fungal metabolism of 5 and 6.
Barrero
A F
AF
Departamento de Química Orgánica, Instituto de Biotecnología, Facultad de Ciencias, Universidad de Granada, Granada, Spain. afbarre@goliat.ugr.es
Oltra
J E
JE
Cerdá-Olmedo
E
E
Avalos
J
J
Justicia
J
J
D001711:Biotransformation; D004224:Diterpenes / Q000378:metabolism*; D005874:Gibberella / Q000235:genetics / Q000378:metabolism*; D006900:Hydroxylation; D008956:Models, Chemical; D009154:Mutation
D004224:Diterpenes; C051436:kaurenoic acid