Apicomplexa form one of the largest and most diverse groups of obligate intracellular parasites, capable of infecting almost every kind of animal. It is estimated that between 1.2 and 10 million species exist, but only about 5,000-6,000 have been identified to date. These include Plasmodium, which that causes malaria and about 440,000 deaths every year, Toxoplasma, which causes congenital disease and opportunistic infections in immunocompromised people, Babesia, which infects cattle, and others. Despite the global economic and health impact of these parasites, much of their biology is still unknown. For example, their surface is covered by glycoconjugates that are essential for their survival and infectivity, but little is known of the processes that lead to the synthesis of such molecules. In particular, one of the enzymes needed for the synthesis of important glycoconjugates had not yet been identified—the apicomplexan organisms do not have the GNA1 enzyme that fulfils this function in animals, plants and other eukaryotes.