title: Differentiation-inducing-factor dechlorinase, a novel cytosolic dechlorinating enzyme from Dictyostelium discoideum.
abstract: Differentiation-inducing factor 1 (DIF-1) is a dichlorinated alkyl phenone (1-[(3,5-dichloro-2,6-dihydroxy-4-methoxy)phenyl]hexan-1-one) from Dictyostelium discoideum, that induces amoebae to differentiate into stalk cells. It was shown previously that DIF-1 is rapidly metabolized into a series of more polar compounds by living cells [Traynor, D. & Kay, R.R. (1991) J. Biol. Chem. 266, 5291-5297]. The first step in DIF-1 metabolism is the formation of DIF metabolite 1 (now known to be DIF-3) by a monodechlorination. We report here the discovery of the enzyme activity catalyzing this dechlorination. A very sensitive enzyme assay was developed, using [3H]DIF-1 and a TLC system to separate DIF-1 from the product, DIF-3. DIF-1 3(5)-dechlorinase is present in the high-speed supernatant of cell lysates, and uses glutathione, at physiological concentrations, as cofactor. Kinetic measurements indicate a Km for DIF-1 of about 70 nM. The enzyme activity is inhibited by DIF-2 (the pentan-1-one analogue of DIF-1), with a median inhibitor concentration (IC50) of 1 microM, and DIF-3 (IC50 = 5 microM), which presumably act as substrates, but other compounds structurally related to DIF-1 were much less effective. Aurothioglucose, an inhibitor of selenocysteine enzymes, inhibited DIF-1 3(5)-dechlorinase with IC50 = 100 nM. DIF-1 3(5)-dechlorinase activity is developmentally regulated. It is essentially absent from growing cells and increases at the end of aggregation to reach a first peak of activity at the first finger stage, with a further rise at culmination.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, England.
authors.forename: O
authors.initials: O
authors.lastname: Nayler
authors.forename: R
authors.initials: R
authors.lastname: Insall
authors.forename: R R
authors.initials: RR
authors.lastname: Kay
mesh_terms: D000818:Animals; D006051:Aurothioglucose / Q000494:pharmacology; D002850:Chromatography, Gel; D002855:Chromatography, Thin Layer; D004023:Dictyostelium / Q000201:enzymology* / Q000254:growth & development; D004492:Edetic Acid / Q000494:pharmacology; D006588:Hexanones / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008190:Lyases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D008970:Molecular Weight; D010088:Oxidoreductases; D013379:Substrate Specificity
chemical_list: C075859:DIF-1 3(5)-dechlorinase; D006588:Hexanones; C053433:1-((3,5-dichloro)-2,6-dihydroxy-4-methoxyphenyl)-1-hexanone; D006051:Aurothioglucose; D004492:Edetic Acid; D010088:Oxidoreductases; D008190:Lyases