Depicting the proton relay network in human aromatase: New insights into the role of the alcohol-acid pair

Human aromatase is the cytochrome P450 catalyzing the conversion of androgens into estrogens in a three steps reaction essential to maintain steroid hormones balance. Here we report the capture and spectroscopic characterization of its compound I (Cpd I), the main reactive species in cytochromes P450. The typical spectroscopic transitions indicating the formation of Cpd I are detected within 0.8 s when mixing aromatase with meta‐chloroperoxybenzoic acid. The estrogen product is obtained from the same reaction mixture, demonstrating the involvement of Cpd I in aromatization reaction. Site‐directed mutagenesis is applied to the acid‐alcohol pair D309 and T310 and to R192, predicted to be part of the proton relay network. Mutants D309N and R192Q do not lead to Cpd I with an associated loss of activity, confirming that these residues are involved in proton delivery for Cpd I generation. Cpd I is captured for T310A mutant and shows 2.9‐ and 4.4‐fold faster rates of formation and decay, respectively, compared to wild‐type (WT). However, its activity is lower than the WT and a larger amount of H(2)O(2) is produced during catalysis, indicating that T310 has an essential role in proton gating for generation of Cpd 0 and Cpd I and for their stabilization. The data provide new evidences on the role of threonine belonging to the conserved “acid‐alcohol” pair and known to be crucial for oxygen activation in cytochromes P450

La capacità repressiva di compost nei confronti della tracheofusariosi del basilico

Alcuni compost, addizionati al suolo o impiegati come componenti di substrati per colture in vaso, possono svolgere un’attività repressiva nei confronti dei patogeni terricoli. Nel biennio 2005-2006 sono stati saggiati, a Grugliasco (TO), in serre in ferro/vetro, compost provenienti da aziende di compostaggio presenti sul territorio piemontese al fine di valutarne la loro capacità repressiva. Dai risultati è emerso l’efficace contenimento nei confronti di F. oxysporum f.sp. basilici, da parte di compost prodotto a partire da rifiuti solidi urbani e fanghi, con una diminuzione fino al 50% di piante morte e un incremento fino al 25% di biomassa prodotta a fine ciclo rispetto a quanto rilevato impiegando un ammendante torboso scelto come riferimento