Arginine:glycine amidinotransferase deficiency  or AGAT deficiency is an autosomal recessive cerebral creatine deficiency caused by a deficiency of the enzyme arginine:glycine amidinotransferase. This enzyme deficiency results in decreased creatine synthesis, and is caused by biallelic pathogenic variants in GATM. Individuals with AGAT deficiency are intellectually disabled and have muscle weakness. The symptoms of AGAT deficiency are caused by the lack of creatine in specific tissues, most notably muscle and brain. Oral creatine supplementation can be used to treat AGAT deficiency, with early intervention providing the best results. All creatine deficiencies are rare, and there have been fewer than 20 individuals reported in medical literature with AGAT deficiency. This disorder was first described in 2000. Signs and symptoms
As with other cerebral creatine deficiency syndromes, individuals affected with AGAT deficiency are intellectually disabled and can have seizures. They can often have muscle weakness. These symptoms are caused by the lack of creatine in skeletal muscles and in the brain. AGAT deficiency was first identified in 2000, in a pair of sisters aged 4 and 6. Both sisters had severe intellectual disability. Genetics
AGAT deficiency is caused by deficient activity of arginine:glycine amidinotransferase, which is coded for by GATM, located on the long arm of chromosome 15. AGAT deficiency is inherited in an autosomal recessive manner, which means pathogenic variants must be inherited from each parent. This enzyme catalyzes the first step in creatine biosynthesis, the combination of arginine and glycine to form guanidinoacetate, which also results in the formation or ornithine as a by product.
Use in biotechnology
Rifampicin inhibits bacterial RNA polymerase, thus it is commonly used to inhibit the synthesis of host bacterial proteins during recombinant protein expression in bacteria. RNA encoding for the recombinant gene is usually transcribed from DNA by a viral T7 RNA polymerase, which is not affected by rifampicin. History
In 1957, a soil sample from a pine forest on the French Riviera was brought for analysis to the Lepetit Pharmaceuticals research lab in Milan, Italy. There, a research group headed by Piero Sensi and Maria Teresa Timbal discovered a new bacterium. This new species produced a new class of molecules with antibiotic activity. Because Sensi, Timbal and the researchers were particularly fond of the French crime story Rififi (about a jewel heist and rival gangs), they decided to call these compounds rifamycins. After two years of attempts to obtain more stable semisynthetic products, a new molecule with high efficacy and good tolerability was produced in 1965 and was named rifampicin.Rifampicin was first sold in Italy in 1968 and was approved by the FDA in 1971. Society and culture
Cancer-causing impurities
In August 2020, the U.S. Food and Drug Administration (FDA) became aware of nitrosamine impurities in certain samples of rifampin. The FDA and manufacturers are investigating the origin of these impurities in rifampin, and the agency is developing testing methods for regulators and industry to detect the 1-methyl-4-nitrosopiperazine (MNP).