Mini-Symposium - Abstracts
8 PHOSPHOLIPASE A2 FROM HYMENOPTERAN VENOMS:BIOCHEMICAL CHARACTERIZATION
M.S. PALMA
, H. COSTA
, M.R. OLIVEIRA
Departament of Biology, Laboratory of Molecular Biology, Institute of Biosciesces, Rio Claro, SP,
The Center for the Study of Venoms and Venomous Animals - São Paulo State University, Rio Claro, SP, Brazil
Hymenoptera venoms are complex mixtures of pharmacologically and biochemically active substances, including proteins (enzymes), peptides and biogenic amines. The most common feature of these venoms are the allergic symptoms that occur after a sting resulting in a IgE-mediated reaction. The antigenic/allergenic composition of hymenopteran venoms have been extensively studied and the phospholipase A2 (PLA2) is recognized as the major allergen. More than 90% of patients that presented wasp or honey bee-venom anaphylaxis have an IgE-antibody response to PLA2. In spite of this, PLA2 from hymenopteran venoms is relatively seldom studied especially those from neotropical species.
In the last five years, we have investigated the PLA2 from the venoms of Brazilian wasps, Polybia paulista (polibitoxins) and Agelaia pallipes pallipes (agelotoxins). In these venoms, PLA2 is present as multiple forms of different MW. Thus, in P. paulista there are four enzymes with apparent MW values from 118 to 132 Kda, presenting very high contents of associated carbohydrates (from 22 to 49% [m/m]). These PLA2 are dimers constituted by different subunits. In A.p. pallipes venom, PLA2 is present in three different molecular aggregation states with MW 14, 42 and 74 KDa, formed by the polymerization of the same monomeric subunit (MW 14 Kda, that presents 22% (m/m) of associated carbohydrates. Each one of the polybitoxins presented different values of Km (changing from 10
to 10
M of phosphatydilcholine) and optimal pH, and all enzymes presented a negative cooperativity kinetics concerning substrate hydrolysis. The agelotoxins presented Michaelian behaviors with a decrease in the Vmax of substrate hydrolysis, as function of enzyme polymerization and different optimal pH value for each different aggregation state.
Both polybitoxins and agelotoxins present hemolytic activities up to 200-fold higher than the PLA2 from Naja nigricolis and Naja n. atra venoms. Preliminary assays demonstrated that all these toxins are myotoxic and some of them are neurotoxic. However, no further investigation was carried out to elucidate the extension and the mechanisms of damage.
Financial support : FAPESP, FUNDUNESP and SUNBOR GRANTS
CORRESPONDENCE TO:
Prof. Dr. Mário Sérgio Palma - Instituto de Biociências, Departamento de Biologia, UNESP, Rio Claro, Avenida 24-A, 1515, Bela Vista, CEP 13500-900, Rio Claro, SP, Brasil. email: mspalma@life.ibrc.unesp.br
Publication Dates
-
Publication in this collection
08 Jan 1999 -
Date of issue
1997
