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Isotope labelling experiments on the formation pathway of 3‐hydroxy‐4,5‐dimethyl‐2(5 H )‐furanone from l ‐isoleucine in cultures of Laetiporus sulphureus
Author(s) -
Lanfermann Isabel,
Krings Ulrich,
Schopp Silke,
Berger Ralf G.
Publication year - 2014
Publication title -
flavour and fragrance journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.393
H-Index - 70
eISSN - 1099-1026
pISSN - 0882-5734
DOI - 10.1002/ffj.3200
Subject(s) - chemistry , isoleucine , leucine , hydroxylation , biotransformation , stereochemistry , food science , amino acid , biochemistry , enzyme
ABSTRACT Sotolon (3‐hydroxy‐4,5‐dimethyl‐2(5 H )‐furanone) imparts a strong seasoning odour reminiscent of meat broth. Previous work indicated a formation via l ‐4‐hydroxyisoleucine in surface cultures of the basidiomycete Laetiporus sulphureus grown on wheat gluten, but an enzymatic hydroxylation of l ‐isoleucine was not proven. 13 C‐Labelled l ‐leucine, l ‐isoleucine and 18 O‐water were used to elucidate the metabolism of the amino acids and proved the existence of an oxygenase activity in the pathway to sotolon. l ‐Isoleucine was converted into the corresponding α ‐keto acid and then oxygenated in the C4‐position to give 4‐hydroxy‐3‐methyl‐2‐oxopentanoic acid, the direct precursor of sotolon. A similar biotransformation was not observed for l ‐leucine. The results provide insight into the cold formation of a potent flavour compound previously associated with the thermal processing of food. Copyright © 2014 John Wiley & Sons, Ltd.