Involvement of g proteins and camp in the production of chitinolytic enzymes by Trichoderma harzianum

The effect of G protein modulators and cyclic AMP (cAMP) on N-acetylglucosaminidase (NAGase) production was investigated during 84 h of growth of a Trichoderma harzianum strain in chitin-containing medium. Caffeine (5 mM), N6¾2'-O-dibutyryladenosine 3'5'-cyclic monophosphate sodium salt (dBcAMP) (1 mM) and 3-isobutyl-1-methylxanthine (IBMX) (2 mM) decreased extracellular NAGase activity by 80(per cent), 77(per cent) and 37(per cent), respectively. AlCl3/KF (100 µM/10 mM and 200 µM/ 20 mM) decreased the activity by 85(per cent)and 95(per cent), respectively. Cholera (10 µ/mL) and pertussis (20 µ/mL) toxins also affected NAGase activity, causing a decrease of approximately 75(per cent). Upon all treatments, protein bands of approximately 73 kDa, 68 kDa and 45 kDa had their signals diminished whilst a 50 kDa band was enhanced only by treatment with cholera and pertussis toxins. N-terminal sequencing analysis identified the 73 kDa and 68 kDa proteins as being T. harzianum NAGase in two different truncated forms whereas the 45 kDa band comprised a T. harzianum endochitinase. The 50 kDa protein showed sequence similarity to Coriolus vesicolor cellobiohydrolase. The above results suggest that a signaling pathway comprising G-proteins, adenylate cyclase and cAMP may be involved in the synthesis of T. harzianum chitinases.

Determinaçäo de albumina humana em soros normais: comparaçäo de três métodos / Determinantion of human albumin in normal sera: comparison of 3 methods

A concentraçäo de albumina em soros de indivíduos normais foi determinada através dos métodos verde de bromocresol (VBC), púrpura de bromocresol (PBC) e imunoturbidimetria (I). A precisäo (Cv) destes métodos, investigada em "pool" de soros normais, foi de 3,6% para o imunoensaio e de 2,8% e 2,5% para o VBC e PBC, respectivamente. Estudos comparativos mostraram que os valores de albumina obtidos pelos métodos colorimétricos foram sistemática e significativamente mais elevados que os determinados por imunoturbidimetria. A PBC proporcionou valores de albumina mais próximos daqueles conferidos pela imunoturbidimetria, corroborando as evidências já apontadas na literatura a cerca da maior especificidade da reaçäo PBC-albumina