Information: - Antifolates are a class of antimetabolite medications that antagonise (that is, block) the actions of folic acid (vitamin B). Folic acid's primary function in the body is as a cofactor to various methyltransferases involved in serine, methionine, thymidine and purine biosynthesis. Consequently, antifolates inhibit cell division, DNA/RNA synthesis and repair and protein synthesis. Some such as proguanil, pyrimethamine and trimethoprim selectively inhibit folate's actions in microbial organisms such as bacteria, protozoa and fungi. The majority of antifolates work by inhibiting dihydrofolate reductase (DHFR). - Cycloguanil is a dihydrofolate reductase inhibitor , and is a metabolite of the antimalarial drug proguanil ; its formation in vivo has been thought to be primarily responsible for the antimalarial activity of proguanil . However , more recent work has indicated that , while proguanil is synergistic with the drug atovaquone ( as in the combination Malarone ) , cycloguanil is in fact antagonistic to the effects of atovaquone , suggesting that , unlike cycloguanil , proguanil may have an alternative mechanism of antimalarial action besides dihydrofolate reductase inhibition . Although cycloguanil is not currently in general use as an antimalarial , the continuing development of resistance to current antimalarial drugs has led to renewed interest in studying the use of cycloguanil in combination with other drugs . - Dihydrofolate reductase, or DHFR, is an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, using NADPH as electron donor, which can be converted to the kinds of tetrahydrofolate cofactors used in 1-carbon transfer chemistry. In humans, the DHFR enzyme is encoded by the "DHFR" gene. It is found in the q11q22 region of chromosome 5. Bacterial species possess distinct DHFR enzymes (based on their pattern of binding diaminoheterocyclic molecules), but mammalian DHFRs are highly similar. - A dihydrofolate reductase inhibitor (DHFR inhibitor) is a molecule that inhibits the function of dihydrofolate reductase, and is a type of antifolate. - Atovaquone (alternative spelling: atavaquone) is a chemical compound that belongs to the class of naphthoquinones. Atovaquone is a hydroxy-1,4-naphthoquinone, an analog of ubiquinone, with antipneumocystic activity. It is manufactured in the US in the liquid form, or oral suspension, under the brand name Mepron. What entity does 'cycloguanil' has the relation 'instance of' with?
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Answer: chemical compound

Information: - In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet about a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating path around a body, although it may occasionally be used for a non recurring trajectory or a path around a point in space. To a close approximation, planets and satellites follow elliptical orbits, with the central mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion. - Union Observatory also known as Johannesburg Observatory (078) is a defunct astronomical observatory in Johannesburg, South Africa that was operated between 1903 and 1971. It is located on Observatory Ridge, the city's highest point at 1,808 metres altitude in the suburb Observatory. - A minor planet is an astronomical object in direct orbit around the Sun that is neither a planet nor exclusively classified as a comet. Minor planets can be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, and other trans-Neptunian objects. As of 2016, the orbits of 709,706 minor planets were archived at the Minor Planet Center, 469,275 of which had received permanent numbers ). - Harry Edwin Wood (3 February 1881 27 February 1946) was an English astronomer, director of the Union Observatory in Johannesburg, and discoverer of minor planets. - 790 Pretoria is a minor planet orbiting the Sun that was discovered by English astronomer Harry Edwin Wood on January 16 , 1912 . It is a member of the Cybele group located beyond the core of the main belt ( see Minor planet groups ) . 10 radiometric data collected from Kitt Peak in 1975 gave a diameter estimate of 175 km. In the present day it is estimated to be 170 km ( 106 mi ) in diameter . Photometric measurements of the asteroid made in 2005 at the Palmer Divide Observatory showed a light curve with a period of 10.370 0.002 hours and a brightness variation of 0.08 0.03 in magnitude . - The Minor Planet Center (MPC) is the official worldwide organization in charge of collecting observational data for minor planets (such as asteroids) and comets, calculating their orbits and publishing this information via the "Minor Planet Circulars". Under the auspices of the International Astronomical Union, it operates at the Smithsonian Astrophysical Observatory, which is part of the Center for Astrophysics along with the Harvard College Observatory. What entity does '790 pretoria' has the relation 'site of astronomical discovery' with?
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Answer:
union observatory