title: Metabolic control analysis of the penicillin biosynthetic pathway: the influence of the LLD-ACV:bisACV ratio on the flux control.
abstract: An extended kinetic model for the first two steps of the penicillin biosynthetic pathway in Penicillium chrysogenum is set up. It includes the formation and reduction of the dimer bis-delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (bisACV) from the first pathway intermediate LLD-ACV and their parallel inhibition of the enzyme ACV synthetase (ACVS). The kinetic model is based on Michaelis-Menten type kinetics, with non-competitive inhibition of the ACVS by both LLD-ACV and bisACV, and competitive inhibition of the isopenicillin N synthetase (IPNS) by glutathione. The inhibition constant of LLD-ACV, KACV is determined to be 0.54 mm. With the kinetic model metabolic control analysis is performed to identify the distribution of rate-control in the pathway at all ratios of LLD-ACV:bisACV. It is concluded that the flux control totally resides at the IPNS. This is a result of the regulation of the ACVS by both the LLD-ACV and bisACV demanding a higher flux through the IPNS enzyme to alleviate their inhibition. The measurement of an intracellular ratio of LLD-ACV:bisACV to be in the range of 1-2 moles per moles emphasises the importance of a fast conversion of LLD-ACV to IPN, and accumulation of LLD-ACV above the K(m)-value of the IPNS should therefore be avoided.
authors.affiliation: Department of Biotechnology, Technical University of Denmark, Lyngby.
authors.forename: H A
authors.initials: HA
authors.lastname: Theilgaard
authors.forename: J
authors.initials: J
authors.lastname: Nielsen
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005978:Glutathione / Q000378:metabolism; D008954:Models, Biological; D009842:Oligopeptides / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000096:biosynthesis*; D010408:Penicillium chrysogenum / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D010453:Peptide Synthases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D009842:Oligopeptides; D046915:Penicillin-Binding Proteins; D010406:Penicillins; C121743:bis(aminoadipyl)-cysteinyl-valine; C011638:5-(2-aminoadipyl)cysteinylvaline; D010088:Oxidoreductases; C038370:isopenicillin N synthetase; D000217:Acyltransferases; C018756:acyl-CoA-6-aminopenicillanic acid acyltransferase; D010453:Peptide Synthases; C095368:alpha-aminoadipyl-cysteinyl-valine synthetase; D005978:Glutathione