{'fraction_non_alphanumeric': 0.032237673830594185, 'fraction_numerical': 0.01580278128950695, 'mean_word_length': 5.942982456140351, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 2, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Regulatory properties of citrate synthase from Rickettsia prowazekii

Citrate synthase [citrate (si)-synthase] (EC 4.1.3.7) was partially purified from extracts of highly purified typhus rickettsiae (Rickettsia prowazekii). Molecular exclusion and affinity column chromatography were used to prepare 200-fold-purified citrate synthase that contained no detectable malate dehydrogenase (EC 1.1.1.37) activity. Rickettsial malate dehydrogenase also was partially purified (200-fold) via this purification procedure. Catalytically active citrate synthase exhibited a relative molecular weight of approximately 62,000 after elution from a calibrated Sephacryl S-200 column. Acetyl coenzyme A saturation of partially purified enzyme was sensitive to strong competitive inhibition with adenylates (ATP greater than ADP much greater than AMP). [beta,gamma-methylene]ATP, dATP, and dADP also caused strong inhibition, but guanosine and cytosine nucleotides were significantly less inhibitory. Adenylates had no effect on oxalacetate saturation kinetics when acetyl coenzyme A was present in high concentration (greater than or equal to 50 microM). Neither NADH nor alpha-ketoglutarate affected the saturation kinetics of rickettsial citrate synthase. Thus, citrate synthase from R. prowazekii exhibits greater similarity to the eucaryotic and gram-positive procaryotic enzymes than to citrate synthase from free-living gram-negative bacteria. These results represent the first characterization of a highly purified key regulatory enzyme from these obligate intracellular parasitic bacteria.