MALATE-DEHYDROGENASE ISOENZYMES FROM MOLINEMA-DESSETAE (NEMATODA, FILARIOIDEA) - IDENTIFICATION AND SURAMIN INHIBITORY EFFECT

High malate dehydrogenase (MDH) activity was detected in the filarial worm Molinema dessetae. The poor mobility of M. dessetae MDH using cla ssical methods led to set up a good separation system. Polyacrylamide disc electrophoresis allowed the detection of two MDH isoenzymes in ma le and female worms. The major form MDH1 (74 +/- 5% of total MDH activ ity in mole and female, m +/- s.e.m., n = 40 for each sex) was found f rom cytoplasmic origin whereas the minor form, MDH2, was mitochondrial (26 +/- 3% in both sexes, m +/- s.e.m., n = 40 for each sex). One mit ochondrial malic enzyme using NAD and NADP was also detected. Gel elec trophoresis in conjunction with densitometry was used to screen MDH in hibitors. Suramin was used as a reference compound. The suramin IC50 v alue obtained from this method was 17.3 +/- 1.2 mu M whereas it was 23 .1 +/- 0.9 mu M by spectrophotometric assay (m +/- s.e.m., n = 5). Alt hough this method and enzyme assay had curves [% activity = f (log con centration)] significantly different, gel densitometry allows the iden tification of a potential selective inhibitory effect towards one isoe nzyme without previous protein purification.