1.Biotransformations catalyzed by cloned p-cymene monooxygenase from Pseudomonas putida F1.
Nishio T1, Patel A, Wang Y, Lau PC. Appl Microbiol Biotechnol. 2001 Apr;55(3):321-5.
p-Cymene monooxygenase (CMO) from Pseudomonas putida F1 consists of a hydroxylase (CymA1) and a reductase component (CymA2) which initiate pcymene (p-isopropyltoluene) catabolism by oxidation of the methyl group to p-isopropylbenzyl alcohol (p-cumic alcohol). To study the possible diverse range of substrates catalyzed by CMO, the cymA1A2 genes were cloned in an Escherichia coli pT7-5 expression system and the cells were used in transformation experiments. The tested substrates include different substituents on the aromatic ring at the 2 (ortho), 3 (meta) or 4 (para) position relative to the methyl moiety. As a result, a distinct preference was observed for substrates containing at least an alkyl or heteroatom substituent at the para-position of toluene. The conversion rate of 4-chlorotoluene or 4-methylthiotoluene to the corresponding benzyl alcohol was found to be as good as the canonical substrate, p-cymene. But 3-chlorotoluene, 4-fluorotoluene and 4-nitrotoluene were relatively poor substrates.
2.p-Cymene catabolic pathway in Pseudomonas putida F1: cloning and characterization of DNA encoding conversion of p-cymene to p-cumate.
Eaton RW1. J Bacteriol. 1997 May;179(10):3171-80.
Pseudomonas putida F1 utilizes p-cymene (p-isopropyltoluene) by an 11-step pathway through p-cumate (p-isopropylbenzoate) to isobutyrate, pyruvate, and acetyl coenzyme A. The cym operon, encoding the conversion of p-cymene to p-cumate, is located just upstream of the cmt operon, which encodes the further catabolism of p-cumate and is located, in turn, upstream of the tod (toluene catabolism) operon in P. putida F1. The sequences of an 11,236-bp DNA segment carrying the cym operon and a 915-bp DNA segment completing the sequence of the 2,673-bp DNA segment separating the cmt and tod operons have been determined and are discussed here. The cym operon contains six genes in the order cymBCAaAbDE. The gene products have been identified both by functional assays and by comparing deduced amino acid sequences to published sequences. Thus, cymAa and cymAb encode the two components of p-cymene monooxygenase, a hydroxylase and a reductase, respectively; cymB encodes p-cumic alcohol dehydrogenase; cymC encodes p-cumic aldehyde dehydrogenase; cymD encodes a putative outer membrane protein related to gene products of other aromatic hydrocarbon catabolic operons, but having an unknown function in p-cymene catabolism; and cymE encodes an acetyl coenzyme A synthetase whose role in this pathway is also unknown.
3.Metabolism of alpha- and beta-pinene, p-cymene and 1,8-cineole in the brushtail possum, Trichosurus vulpecula.
Southwell IA, Flynn TM, Degabriele R. Xenobiotica. 1980 Jan;10(1):17-23.
1. The nature of the non-conjugated metabolites of the Eucalyptus oil terpenoid components alpha-pinene, beta-pinene, p-cymene and 1,8-cineole in the urine and faeces of the brushtail possum was investigated. 2. alpha-Pinene was metabolized to myrtenic acid and trans-verbenol, beta-pinene to myrtenic acid, p-cymene to p-cresol and cumic acid, and 1,8-cineole to p-cresol, 9-hydroxycineole and cineol-9-oic acid.
4.p-Cymene metabolism in rats and guinea-pigs.
Walde A, Ve B, Scheline RR, Monge P. Xenobiotica. 1983 Aug;13(8):503-12.
The metabolism of p-cymene was studied in rats and guinea-pigs. Following intragastric or inhalation dosage (100 mg/kg) urinary metabolite excretion was nearly complete within 48 h, amounting to 60-80% dose. The inhalation experiments gave the lowest values. 18 urinary metabolites were detected and identified. Of these, rats did not excrete two and guinea-pigs did not excrete a third. No ring-hydroxylation of p-cymene was detected in rats, but guinea-pigs formed small amounts of carvacrol and hydroxycarvacrol. Oxidation of both the methyl and isopropyl groups of p-cymene occurred extensively in both species. The following types of metabolites were formed: monohydric alcohols, diols, mono- and di-carboxylic acids and hydroxyacids. Conjugation with glycine of the cumic acid formed was extensive in guinea-pigs.