Distribution of chitinase in guinea pig tissues and increases in levels ofthis enzyme after systemic infection with Aspergillus fumigatus

Intravenous infection of guinea pigs with the fungus Aspergillus fumigatus resulted in increased levels of chitinase in serum and tissues of the anima ls. The molecular properties of the enzyme were demonstrated to be differen t from those of the fungal chitinase, but also from guinea pig lysozyme and beta-N-acetylhexosaminidase. Bio-Cel P-100 gel filtration showed that in l iver, spleen, heart and lung tissue of control animals there were two molec ular mass forms present with apparent molecular masses of 35 kDa and 15 kDa , In brain and serum, only the 35 kDa form was detectable. Kidney showed on ly the 15 kDa form. Upon infection the 35 kDa form appeared in kidney and i ncreased in the other tissues. When a less pathogenic form of the fungus wa s used the 35 kDa form remained absent in kidney. In contrast to human seru m chitinase, the enzyme from guinea pig serum and tissues did bind to conca navalin A-Sepharose. This was the case for both molecular mass forms. The m ode of cleavage of the substrate 4-methylumbelliferyl-tri-N-acetylchitotrio side (MU-[GlcNAc](3), where GlcNAc is N-acetylglucosamine) by the two forms of the enzyme was the same: both [GlcNAc](2) and [GlcNAc](3) were released . The chitinase activity levels in the control tissues showed a large varia tion in this order: spleen > lung, kidney > liver,heart > brain. The fact t hat spleen showed the highest chitinase level is in agreement with its majo r role as a lymphoid organ in cases of systemic infections, The relative in creases upon infection were the highest for the tissues that showed low con trol values.