Biochemical properties of trypanosomatid lactate dehydrogenases

Lactate dehydrogenase (LDH, E.C.1.1.1.27) was found in supernatant (cytoplasmic enzyme) fractions of the trypanosomatid flagellates Trypanosoma conorhini and Crithidia fasciculata if 10 mm cysteine was present in the homogenizing medium. The T. conorhini LDH activity with pyruvate as substrate was increased 35% if 5 mm cysteine was also included in reaction mixtures. K(m) values for the T. conorhini enzyme were 3.3 x 10(-4)m with pyruvate, and 1.6 x 10(-4)m with alpha-ketobutyrate. Cysteine inhibited alpha-ketobutyrate reduction. Comparison of trypanosomatid and human serum LDH enzymes with respect to K(m), substrate activity and inhibition, pH optima, and K(i) values for oxalate and oxamate indicated that the trypanosomatid isoenzymes differed significantly from serum LDH. C. fasciculata LDH was extremely labile, since 59% of the activity was lost 90 min after isolation. The role of LDH enzymes in trypanosomatid metabolism is discussed, and the results are related to other trypanosomatid LDH enzymes. The comparison of homologous enzymes in host and parasite is discussed with regard to metabolic function and a possible model system for chemotherapy.

The reversal of Dalapon toxicity by microbial action

A Micrococcus sp., similar to M. flavus, was found to reverse the inhibitory effects of 2,2-dichloropropionic acid (Dalapon) on an unidentified Agarbacterium sp. Neither organism could be shown to degrade the herbicide, as determined by Cl− release or disappearance of the agent from the medium. Bioassay of the filtered micrococcal broth revealed the presence of pantothenic acid. β-Alanine, valine, and alpha-ketoisovalerate could not overcome the herbicide's inhibitory effects on the Agarbacterium, but sodium pamoate produced a slight increase in growth. Calcium pantothenate (0.05 ug/ml) allowed the same amount of growth of the Agarbacterium in Dalapon medium as did the micrococcal filtrate. The finding suggests that an "associative action" of microorganisms may play an important role in microbial resistance to herbicides.

Keto acids as growth-limiting factors in autotrophic growth of Thiobacillus thiooxidans

When the strictly autotrophic bacterium Thiobacillus thiooxidans was grown on sulfur, keto acids accumulated in the medium until they reached an inhibitory level at which growth ceased. Much greater growth was possible if these substances were continually dialyzed out of the medium.

Alpha-hydroxy acid oxidase: localization in renal microbodies

Differential and density equilibrium centrifugation have established the presence of alpha-hydroxy acid oxidase in microbodies of the kidney of the rat. The enzyme has been demonstrated in cells of the distal convoluted tubule by a microscopic cytochemical method. This enzyme, like certain others in microbodies, produces hydrogen peroxide.