Glutathione-S-transferases from chloroquine-resistant and -sensitive strains of Plasmodium falciparum: what are their differences?

Glutathione-S-transferases (GSTs) from chloroquine-resistant (CQR, K1) and -sensitive (CQS, T9/94) strains of Plasmodiumfalciparum were studied. The enzymes from both strains exhibited the optimal pH for enzyme catalysis, at pH 7.5, and were stable at temperatures below 60 degrees C. They also showed the highest specific activities toward CDNB and moderate activities to ethacrynic acid (40% of the activity to CDNB) but little or no activity for other substrates. Km and Vmax values for CDNB and GSH, calculated by Lineweaver-Burk plot from both CQR- and CQS-GSTs, were not statistically different (p<0.05). However, the GSTs activity from CQR appeared to be significantly higher than that from CQS. Therefore, we proposed that GSTs from both malarial strains are identical in their functional domain but different in level of gene expression. Furthermore, protein sequence alignment between P. falciparum GST and GSTs from other organisms suggested that the malarial enzyme is closely similar to other GSTs in Sigma, Alpha, Mu and Pi subclasses, probably most to the Alpha group. Characterization of the purified malarial GST in detail would reveal more precise classification and better understanding of its role in malarial detoxification.

Molecular examination of GH gene deletion in familial growth hormone deficiency.

The human growth hormone gene (GH gene) from nine members of a family with familial growth hormone deficiency was examined. The patients were diagnosed as having growth hormone deficiency clinically and by response to hormonal treatment. PCR amplification was carried out using total DNA extracted from leukocytes. The flanking regions of the GH gene which are highly homologous were amplified by one pair of primers. PCR products of 1900 bp and 1919 bp were obtained. By using the combination of restriction enzymes BgII, HaeII and SmaI to digest these PCR products, the various sizes of GH gene deletion can be detected. None of the possible deletions was found in these patients and their relatives by either PCR or Southern blot analysis.