LEU4

LEU4 is a gene found in the yeast Saccharomyces cerevisiae. It encodes a protein that plays a crucial role in leucine biosynthesis. Specifically, LEU4 is responsible for catalyzing the first committed step in the pathway, which is the condensation of acetyl-CoA and alpha-ketobutyrate to form alpha-ketoisovalerate. This enzyme is also known as alpha-ketoisovalerate synthase.

The LEU4 gene is essential for yeast to synthesize leucine, an essential amino acid. When the LEU4 gene is mutated or deleted, yeast cells are unable to produce leucine and require its addition to the growth medium for survival. This auxotrophy is a common tool used in genetic research involving yeast. The LEU4 protein is a member of the alpha-keto acid reductase family.

Regulation of LEU4 expression is linked to the intracellular concentration of leucine. High levels of leucine lead to decreased transcription of the LEU4 gene, a feedback mechanism that prevents overproduction of the amino acid. Conversely, leucine starvation results in increased LEU4 expression. The protein itself is localized to the cytoplasm. Studies on LEU4 have contributed to our understanding of amino acid biosynthesis pathways and metabolic regulation in eukaryotes.