Phytomonas: relationship between biosynthetic pathway, polyamine contents and transport of precursors

MARCORA MS; CARRILLO C; GONZÁLEZ NS; ZADIKIAN C

San Miguel de Tucumán, Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Bioquímica (SAIB); 2009

SAIB

%">Marcora M.Silvina1, Carrillo Carolina1,2, Gonzalez, Nélida S1, Zadikian Carlos1 y Algranati Israel Fundación Instituto Leloir; QB-FCEN, UBA>Polyamines (putrescine and spermidine) are essential for cell survival and proliferation. Putrescine can be synthesized: a)-from ornithine (orn) by ornithine decarboxylase (ODC); or b)-from arginine (arg), indirectly, by arginine decarboxylase (ADC) or by arginase. Spermidine is formed from putrescine via spermidine synthase. In vivo assays with Phytomonas Jma 066, a plant parasite, have shown that both arg and orn are precursors of putrescine synthesis. However, arg was only converted into orn, indicating the presence of arginase activity, the absence of ADC and that polyamines are synthesized via ODC in Phytomonas. The ODC activity was dependant on the growth phase, being 6.4 and 0.7nmol.h-1.mg-1prot at early log and late phases, respectively. At stationary phase endogenous Spermidine, detected by HPLC, and growth rates were both reduced. Arg and orn were taken up at a rate of 7.6 and 0.84pmol.min-1.10-7cells respectively. Arg competed with orn uptake but the latter did not affect the arg transport. This suggests that they share a transporter with a higher affinity for arg. Lysine was also decarboxylated by ODC (at a rate 100 times lower than orn) and was taken up at 6 pmol.min-1.10-7cells showing no competence by the orn uptake. This work confirms that levels of polyamines and transport of precursors, as well as ODC activity are involved in cell proliferation of Phytomonas Jma 066.