The most recently discovered amino acid, pyrrolysine, is produced by a series of just three chemical reactions with a single precursor – the amino acid lysine, according to new research. Scientists at Ohio State University used mass spectrometry and a series of experiments to discover how cells make the amino acid, a process that until now had been unknown. They confirmed that pyrrolysine is made from enzymatic reactions with two lysine molecules – a surprising finding, given that some portions of its structure suggested to researchers that it might have more complex origins. The research is published in the March 31 issue of the journal Nature. Pyrrolysine is rare and so far is known to exist in about a dozen organisms. But its discovery in 2002 as a genetically encoded amino acid in methane-producing microbes raised new questions about the evolution of the genetic code. Pyrrolysine is among 22 amino acids that are used to create proteins from the information stored in genes. Proteins are essential to all life and perform most of the work inside cells. This information about how pyrrolysine is produced – its biosynthetic pathway – offers a more complete understanding of how amino acids are made. And because of its rarity, this molecule is emerging as a handy tool for manipulating proteins in biomedical research. With its production mechanism identified, scientists can use that information to devise ways to mass-produce similar or identical synthetic molecules for a variety of research purposes. The Ohio State scientists had a genuine "ah-ha" moment over the course of the study. As part of their experimentation, they combined lysine with one other amino acid and some enzymes and expected this to produce what is called an intermediate – essentially, a piece of an amino acid that is generated in the biosynthesis process.
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