LEU9/YOR108W Summary Help

Standard Name LEU9 1
Systematic Name YOR108W
Feature Type ORF, Verified
Description Alpha-isopropylmalate synthase II (2-isopropylmalate synthase); catalyzes the first step in the leucine biosynthesis pathway; the minor isozyme, responsible for the residual alpha-IPMS activity detected in a leu4 null mutant; LEU9 has a paralog, LEU4, that arose from the whole genome duplication (1, 2 and see Summary Paragraph)
Name Description LEUcine biosynthesis 1
Chromosomal Location
ChrXV:523027 to 524841 | ORF Map | GBrowse
Gene Ontology Annotations All LEU9 GO evidence and references
  View Computational GO annotations for LEU9
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 7 genes
Classical genetics
Large-scale survey
80 total interaction(s) for 60 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 9
  • Affinity Capture-RNA: 1
  • Two-hybrid: 3

Genetic Interactions
  • Negative Genetic: 58
  • Positive Genetic: 7
  • Synthetic Growth Defect: 2

Expression Summary
Length (a.a.) 604
Molecular Weight (Da) 67,200
Isoelectric Point (pI) 6.75
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXV:523027 to 524841 | ORF Map | GBrowse
This feature contains embedded feature(s): YOR108C-A
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1815 523027..524841 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000005634

LEU4 and LEU9 encode alpha-isopropylmalate synthase, the enzyme that catalyzes the conversion of 2-keto-isovalerate into alpha-isopropylmalate (3, 1 and reviewed in 4). This reaction is the first step in leucine biosynthesis (see pathway diagram). Leu4p and Leu9p are 83% identical; Leu4p is the major isozyme (1), accounting for about 80% of total alpha-isopropylmalate synthase activity in wild-type cells (5).

Leu9p is localized to the mitochondrial matrix, where the majority of alpha-isopropylmalate synthesis occurs (6, 7). The enzyme is less sensitive to feedback inhibition by leucine than Leu4p which is most likely due to amino acid differences in the 39-amino acid C-terminal regulatory region of the two proteins (1 and references therein).

leu9 deletion strains are still able to grow in the absence of leucine due to redundant Leu4p activity, but cells lacking both enzymes are leucine auxotrophs. In contrast to Leu4p, the presence of Leu9p is not required for normal growth on non-fermentable carbon sources (1).

Last updated: 2006-08-08 Contact SGD

References cited on this page View Complete Literature Guide for LEU9
1) Casalone E, et al.  (2000) Identification by functional analysis of the gene encoding alpha-isopropylmalate synthase II (LEU9) in Saccharomyces cerevisiae. Yeast 16(6):539-45
2) Byrne KP and Wolfe KH  (2005) The Yeast Gene Order Browser: combining curated homology and syntenic context reveals gene fate in polyploid species. Genome Res 15(10):1456-61
3) Chang LF, et al.  (1984) Cloning and characterization of yeast Leu4, one of two genes responsible for alpha-isopropylmalate synthesis. Genetics 108(1):91-106
4) Kohlhaw GB  (2003) Leucine biosynthesis in fungi: entering metabolism through the back door. Microbiol Mol Biol Rev 67(1):1-15, table of contents
5) Chang LF, et al.  (1985) Total deletion of yeast LEU4: further evidence for a second alpha-isopropylmalate synthase and evidence for tight LEU4-MET4 linkage. Gene 33(3):333-9
6) Ryan ED, et al.  (1973) Subcellular localization of the leucine biosynthetic enzymes in yeast. J Bacteriol 116(1):222-5
7) Prohl C, et al.  (2001) The yeast mitochondrial carrier Leu5p and its human homologue Graves' disease protein are required for accumulation of coenzyme A in the matrix. Mol Cell Biol 21(4):1089-97