Biomedical subjects

J K Bhattacharjee

Publications and source records attributed to J K Bhattacharjee.

At least 37 records · Page 2Linked to original sources

PubMed1998

Nucleotide sequence of the Schizosaccharomyces pombe lys1+ gene and similarities of the lys1+ protein to peptide antibiotic synthetases.

The 4.2 kbp lys1+ gene of Schizosaccharomyces pombe encoding the large subunit of alpha-aminoadipate reductase (EC1.2.1.31), an enzyme specific to lysine synthesis in higher fungi, was completely sequenced at the nucleotide level from pLYS1H. The S. pombe lys1+ gene product consists of 1415 amino acid residues and has a putative molecular weight of 155.8 kDa. The encoded protein converts alpha-aminoadipic acid to alpha-aminoadipate-delta-semialdehyde by an ATP-mediated adenylation. Analysis of the sequence showed that the putative protein encoded by lys1+ shares strong homology with the peptide antibiotic synthetases which also use in adenylation step.

Aldehyde Oxidoreductases↗

PubMed1998

A unique fungal lysine biosynthesis enzyme shares a common ancestor with tricarboxylic acid cycle and leucine biosynthetic enzymes found in diverse organisms.

Fungi have evolved a unique alpha-amino-adipate pathway for lysine biosynthesis. The fungal-specific enzyme homoaconitate hydratase from this pathway is moderately similar to the aconitase-family proteins from a diverse array of taxonomic groups, which have varying modes of obtaining lysine. We have used the similarity of homoaconitate hydratase to isopropylmalate isomerase (serving in leucine biosynthesis), aconitase (from the tricarboxylic acid cycle), and iron-responsive element binding proteins (cytosolic aconitase) from fungi and other eukaryotes, eubacteria, and archaea to evaluate possible evolutionary scenarios for the origin of this pathway. Refined sequence alignments show that aconitase active site residues are highly conserved in each of the enzymes, and intervening sequence sites are quite dissimilar. This pattern suggests strong purifying selection has acted to preserve the aconitase active site residues for a common catalytic mechanism; numerous other substitutions occur due to adaptive evolution or simply lack of functional constraint. We hypothesize that the similarities are the remnants of an ancestral gene duplication, which may not have occurred within the fungal lineage. Maximum likelihood, neighbor joining, and maximum parsimony phylogenetic comparisons show that the alpha-aminoadipate pathway enzyme is an outgroup to all aconitase family proteins for which sequence is currently available.

Aconitate Hydratase↗

PubMed1998

Molecular analysis of the LYS2 gene of Candida albicans: homology to peptide antibiotic synthetases and the regulation of the alpha-aminoadipate reductase.

The unique alpha-aminoadipate pathway for lysine biosynthesis is present only in fungi and involves eight enzyme steps. alpha-Aminoadipate semialdehyde dehydrogenase, commonly called alpha-aminoadipate reductase (AAR), catalyzes the conversion of alpha-aminoadipic acid to alpha-aminoadipic semialdehyde by a novel mechanism. Two genes, LYS2 and LYS5, encode the heterodimeric enzyme in Saccharomyces cerevisiae. The LYS2 gene of Candida albicans was shown to be contained in the 4.8-kb insert of the plasmid pCaLYS2. This plasmid complemented lys2 mutants of both S. cerevisiae and C. albicans. The S. cerevisiae and C. albicans Lys2(+) transformants exhibited 138% and 160% of wild-type AAR activity, respectively. The DNA-sequence analysis of the 4.8-kb region in plasmid pCaLYS2 and a PCR product from genomic DNA which overlapped with the 4.8-kb insert revealed a continuous ORF of 4173 nucleotides encoding 1391 amino-acid residues. The C. albicans LYS2 ORF exhibited 63.0% identity at the nucleotide level and 56.2% identity at the amino-acid level to the LYS2 gene of S. cerevisiae. The ORF is preceded by consensus sequences for the TATA-, CAAT- and GCN4-box elements. An S. cerevesiae-type transcription termination signal is seen in the 3' flanking region. The deduced amino-acid sequence revealed a motif for an AMP-binding site and also the highly conserved core sequences common to peptide antibiotic synthetases. The LYS2 mRNA and alpha-aminoadipate reductase activity were repressed to a higher level in YEPD-grown cells than in cells grown in the presence of lysine or minimal medium. Additionally, AAR was shown to be feedback-inhibited by lysine and the lysine analog, thialysine. The results of the present report reveal the molecular characteristics of the LYS2 gene of C. albicans, its homology to peptide antibiotic synthetases, its divergence from the LYS2 gene of S. cerevisiae, and the regulation of AAR in C. albicans.

Aldehyde Oxidoreductases↗

PubMed1996

The LYS5 gene of Saccharomyces cerevisiae.

The LYS2 and LYS5 genes of Saccharomyces cerevisiae together encode the 180-kDa alpha-aminoadipate reductase (AAR) in the biosynthetic pathway of lysine. The 4.8-kb LYS2 gene encodes the 155-kDa subunit of AAR. The complete nucleotide (nt) sequence of the 1.1-kb LYS5 gene is presented in this report. It contains a single continuous open reading frame of 816 nt encoding a 272-amino-acid, 30.6-kDa polypeptide.

Aldehyde Oxidoreductases↗

PubMed1995

Molecular properties of the lys1+ gene and the regulation of alpha-aminoadipate reductase in Schizosaccharomyces pombe.

The alpha-aminoadipate pathway for the biosynthesis of lysine is unique to fungi. Molecular properties of the cloned lys1+ gene and the regulation of the encoded alpha-aminoadipate reductase (AAR) were investigated in the fission yeast Schizosaccharomyces pombe. A 5.2-kb HindIII-EcoRI fragment of S. pombe DNA, containing a functional lys1+ gene and a promoter, was subcloned to make the 10.7-kb plasmid pLYS1H. A nested 1.778-kb HindIII-EcoRI DNA fragment that complemented the lys1-131 mutant phenotype was sequenced from the plasmid pLYS1D, and shown to contain an open reading frame (ORF) of 470 amino acids, preceded by putative POLII promoter elements (TATA and CCAAT box elements, and two potential yeast GCN4-binding motifs) within 368 bp upstream of the start codon. This ORF shared with the corresponding region of the isofunctional AAR of Saccharomyces cerevisiae 49% amino-acid identity (62% similarity) overall, within which were smaller regions of marked sequence conservation. One such region coincided (95% identity) with a putative AMP-binding domain motif identified in the AAR of S. cerevisiae. In wild-type S. pombe, AAR activity from cells grown in lysine-supplemented minimal or YEPD media was less than the activity of cells grown in minimal medium. The AAR of S. pombe was more sensitive to feedback inhibition by lysine in vitro than the AAR of S. cerevisiae. These results show the effects of extensive evolutionary divergence on the structure and expression of a pivotal enzyme in the alpha-aminoadipate pathway. Presumably, delineated regions of strong sequence conservation correspond to discrete domains essential to AAR function.

Aldehyde Oxidoreductases↗

PubMed1994

Molecular and functional analysis of the LYS1 gene of Candida albicans.

The LYS1 gene of Candida albicans has been localized to a 1.8-kb DNA fragment present on the plasmid YpBRG2. YpBRG2 has been shown to complement the saccharopine dehydrogenase mutant Stx4-4A of Saccharomyces cerevisiae. Transformants of S. cerevisiae Stx4-4A exhibited significant saccharopine dehydrogenase activity, and cells that had lost YpBRG2 after nonselective growth had no enzyme activity. The DNA sequence of the LYS1 gene has been determined. The LYS1 DNA contains typical yeast upstream regulatory sequences, including the GCN4 motif and candidate sequences responsible for transcription termination within the 3' noncoding region. The fragment contained an open reading frame of 1,146 nucleotides coding for a putative protein of 382 amino acids. The open reading frame has 60% identity at the nucleotide level and 71% similarity at the amino acid level to the LYS5 gene of Yarrowia lipolytica, which is believed to code for saccharopine dehydrogenase. A peptide of 11 amino acids has been found, which is present in S. cerevisiae, Y. lipolytica, and C. albicans. This peptide can be expanded to 16 amino acids when the sequences from Y. lipolytica and C. albicans are compared. A motif responsible for the binding of the adenosine residue of NADH has been described previously and is very similar to this peptide, which may be the site of NADH binding in the saccharopine dehydrogenase of C. albicans.

Amino Acid Sequence↗

PubMed1993

Physical and functional characterization of the cloned lys1+ gene of Schizosaccharomyces pombe.

The alpha-aminoadipate pathway for the biosynthesis of lysine is present in yeast and other higher fungi. The lys2 and lys5 mutants of Saccharomyces cerevisiae as well as the lys1- and lys7-mutants of Schizosacharomyces pombe are blocked at the alpha-aminoadipate reductase step of this pathway. The cloned lys1+ gene in the plasmid pLYS1 isolated from a S. pombe genomic library complemented lys1-mutant of S. pombe. The cloned LYS2 gene in the plasmid YEp620 and the LYS5 gene in the plasmid pSC5 of S. cerevisiae exhibited heterologous complementation of lys1- and lys7-mutants, respectively, of S. pombe. The homologous lys1+ transformed cells exhibited five fold higher alpha-aminoadipate reductase activity while the heterologous lys1+ and lys7+ transformed cells exhibited much less activity than the wild type cells. The DNA insert of the plasmid pLYS1 was determined to be 16.7 kb long and the lys1+ gene has been subcloned within a 9.1 kb Clal-Clal DNA insert of the recombinant plasmids pLYS1B and pLYS1C. The restriction pattern for 12 enzymes of the 9.1 kb DNA insert, (Apal, Aval, BamHI, Clal, EcoRI, EcoRV, HindIII, Hpal, Pstl, Pvull, Sphl, and Xbal), exhibited no obvious similarity to that of the LYS2 gene of S. cerevisiae. A 1.7 kb EcoRI-HindIII DNA fragment of pLYS1B and pLYS1C complemented the lys1-131 mutation in an integrative transformation. Although the lys1+ gene of S. pombe is isofunctional to the LYS2 gene of S. cerevisiae, the restriction sites, and expression of these two genes exhibited considerable divergence.

Aldehyde Oxidoreductases↗

PubMed1992

Physical and biochemical characterization of the cloned LYS5 gene required for alpha-aminoadipate reductase activity in the lysine biosynthetic pathway of Saccharomyces cerevisiae.

The LYS5 and LYS2 genes of Saccharomyces cerevisiae are required for the synthesis of alpha-aminoadipate reductase in the lysine pathway. The LYS5 gene, originally cloned as a DNA insert of the plasmid pSC5, has been subcloned on a 3.2 kb SphI-Sau3AI DNA fragment of the recombinant plasmid pSR7. An internal 2.1 kb HpaI-HpaI DNA fragment of the subclone, upon Southern hybridization, exhibits homology with HpaI-restricted wild-type S. cerevisiae genomic DNA. The lys5+ transformants exhibited alpha-aminoadipate reductase activity similar to that of wild-type cells. S1 nuclease analysis localizes the transcription initiation site relative to the detailed restriction map, and reveals the direction of transcription, as well as the transcript size of the LYS5 gene which can be no greater than 1.65 kb. From this it is estimated that the encoded polypeptide is appreciably smaller than the 4 kb LYS2 gene product. These results provide a physical and biochemical characterization of the cloned LYS5 gene. Based on these observations, it is concluded that the LYS5 gene encodes a relatively small polypeptide of the large heteropolymeric alpha-aminoadipate reductase.

Aldehyde Oxidoreductases↗

PubMed1992

Lysine biosynthesis in selected pathogenic fungi: characterization of lysine auxotrophs and the cloned LYS1 gene of Candida albicans.

The alpha-aminoadipate pathway for the biosynthesis of lysine is present only in fungi and euglena. Until now, this unique metabolic pathway has never been investigated in the opportunistic fungal pathogens Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. Five of the eight enzymes (homocitrate synthase, homoisocitrate dehydrogenase, alpha-aminoadipate reductase, saccharopine reductase, and saccharopine dehydrogenase) of the alpha-aminoadipate pathway and glucose-6-phosphate dehydrogenase, a glycolytic enzyme used as a control, were demonstrated in wild-type cells of these organisms. All enzymes were present in Saccharomyces cerevisiae and the pathogenic organisms except C. neoformans 32608 serotype C, which exhibited no saccharopine reductase activity. The levels of enzyme activity varied considerably from strain to strain. Variation among organisms was also observed for the control enzyme. Among the pathogens, C. albicans exhibited much higher homocitrate synthase, homoisocitrate dehydrogenase, and alpha-aminoadipate reductase activities. Seven lysine auxotrophs of C. albicans and one of Candida tropicalis were characterized biochemically to determine the biochemical blocks and gene-enzyme relationships. Growth responses to alpha-aminoadipate- and lysine-supplemented media, accumulation of alpha-aminoadipate semialdehyde, and the lack of enzyme activity revealed that five of the mutants (WA104, WA153, WC7-1-3, WD1-31-2, and A5155) were blocked at the alpha-aminoadipate reductase step, two (STN57 and WD1-3-6) were blocked at the saccharopine dehydrogenase step, and the C. tropicalis mutant (X-16) was blocked at the saccharopine reductase step. The cloned LYS1 gene of C. albicans in the recombinant plasmid YpB1078 complemented saccharopine dehydrogenase (lys1) mutants of S. cerevisiae and C. albicans. The Lys1+ transformed strains exhibited significant saccharopine dehydrogenase activity in comparison with untransformed mutants. The cloned LYS1 gene has been localized on a 1.8-kb HindIII DNA insert of the recombinant plasmid YpB1041RG1. These results established the gene-enzyme relationship in the second half of the alpha-aminoadipate pathway. The presence of this unique pathway in the pathogenic fungi could be useful for their rapid detection and control.

Candida albicans↗

PubMed1991

Use of alpha-aminoadipate and lysine as sole nitrogen source by Schizosaccharomyces pombe and selected pathogenic fungi.

alpha-Aminodipate, an intermediate of the lysine biosynthetic pathway of fungi, or lysine when used as the sole nitrogen source in the medium was growth inhibitory and toxic to Saccharomyces cerevisiae. The fission yeast Schizosaccharomyces pombe and pathogenic fungi Candida albicans, Filobasidiella neoformans and Aspergillus fumigatus grew in the medium containing alpha-aminoadipate as the sole nitrogen source. C. albicans, A. fumigatus, and one of the strains of F. neoformans also grew in the medium containing lysine as the sole nitrogen source. When grown in the alpha-aminoadipate medium, only S. pombe accumulated a significant amount of alpha-ketoadipate in the culture supernatant. Also, 14C-alpha-aminoadipate was converted to 14C-alpha-ketoadipate in vivo. In the ammonium sulfate medium, S. pombe cells converted 14C-alpha-aminoadipate to lysine. The levels of glutamate-alpha-ketoadipate transaminase, an enzyme responsible for the conversion of alpha-aminoadipate to alpha-ketoadipate, and alpha-aminoadipate reductase, an enzyme required for the conversion of alpha-aminoadipate to lysine, were similar in S. pombe cells grown in the alpha-aminoadipate or ammonium sulfate medium. However, the level of homoisocitrate dehydrogenase, an enzyme before the alpha-ketoadipate step, was twelvefold lower in S. pombe cells grown in the alpha-aminoadipate medium compared to the level in cells grown in the ammonium sulfate medium. Pathogenic fungi used in this study did not accumulate alpha-ketoadipate and alpha-aminoadipate-delta-semialdehyde when grown in medium containing alpha-aminoadipate and lysine, respectively, as sole nitrogen source. However, only pathogenic fungi used both lysine and alpha-aminoadipate as sole nitrogen source. This unique metabolic property could be useful for the identification of these pathogens.

2-Aminoadipic Acid↗

PubMed1989

Properties of revertants of lys2 and lys5 mutants as well as alpha-aminoadipate-semialdehyde dehydrogenase from Saccharomyces cerevisiae.

alpha-Aminoadipate-semialdehyde dehydrogenase catalyzes the conversion of alpha-aminoadipate to alpha-aminoadipate-semialdehyde in the biosynthetic pathway of lysine in yeasts and molds. Mutants belonging to lys2 and lys5 loci of Saccharomyces cerevisiae lacked the alpha-aminoadipate-semialdehyde dehydrogenase activity. Complementation in vitro was demonstrated by combining the extracts from different lys2 and lys5 mutants. Some of the revertants of lys2 and lys5 mutants exhibited lower specific activity and higher thermolability of alpha-aminoadipate-semialdehyde dehydrogenase than the enzyme from wild-type cells. The enzyme was partially purified from wild-type cells and the molecular weight of the enzyme was estimated on a Sephacryl S-300 column at 180,000. Results from the revertant analysis and in vitro complementation indicated LYS2 and LYS5 as structural genes, each encoding a subunit of this large enzyme.

Aldehyde Oxidoreductases↗

PubMed1989

Cloning and physical characterization of linked lysine genes (lys4, lys15) of Saccharomyces cerevisiae.

The plasmid pSC4 which carries a 7.8 kb yeast DNA insert at the BamHI site of the Vector YEp13, complemented simultaneously MO-59-13c lys4, LU75 lys15 and LU32 lys4lys15 (double) mutations of Saccharomyces cerevisiae. The 1.9 kb BamHI-XbaI DNA insert of the subclone pSO51 complemented the LU75 lys15 mutation. The 2.8 kb Xhol-XhoI DNA insert of the pSO52 subclone, like pSC4, complemented all three mutations. The 1.9 kb BamHI-XbaI DNA and the 2.8 kb Xhol-XhoI DNA were 100 bp apart in the pSC4 DNA insert and exhibited no homology with each other upon Southern hybridization. The 1.9 kb BamHI-XbaI DNA insert exhibited homology with the pSC4 and pSO51 DNA as well as the genomic DNA of MO-59-13c lys4, LU75 lys15, LU32 lys4lys15, and RC1 (LYS) when digested with appropriate restriction enzymes. The 2.8 kb XhoI-XhoI DNA insert exhibited homology with the pSC4 and pSO52 DNA as well as MO-59-13c lys4, LU75 lys15, LU32 lys4lys15, and RC1 (LYS) genomic DNA, when digested with XhoI enzyme. The 2.8 kb DNA probe also hybridized with ply(A)+ RNA from RC1 and lys4+ transformant but not that from MO-59-13c lys4 mutant.

Blotting, Northern↗

PubMed1988

Cloning and biochemical characterization of LYS5 gene of Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the functions of two unlinked genes (LYS2 and LYS5) are required for the synthesis of the lysine biosynthetic enzyme, alpha-aminoadipate reductase. The LYS5 gene of S. cerevisiae was cloned by functional complementation of a lys5 mutant, X4004-3A, using a YEp24 plasmid library. The cloned LYS5 gene was contained within a 7.5 kb DNA insert of the recombinant plasmid pSC5. Cloning of LYS5 gene was confirmed by second cycle transformation of a lys5 mutant with the pSC5 plasmid, growth response studies, and plasmid loss experiments with Lys5+ transformants. Analysis of restriction digests of the pSC5 plasmid revealed 3 EcoRI, 5 PvuII, 1 PstI, 1 BglII and 2 HpaI sites in the 7.5 kb insert. A 3.9 kb internal pSC5 fragment hybridized only to the plasmid pSC5, but no homology was observed with LYS2 DNA or the YEp24 vector. The pSC5 transformed Lys5+ cells and the wild-type strain exhibited same level of alpha-aminoadipate reductase activity, whereas lys5 mutant and plasmid-cured transformed strain exhibited none. Lys2+ transformants consistently had five times greater alpha-aminoadipate reductase activity when compared with the wild-type and the Lys5+ transformant. The alpha-aminoadipate reductase activity was repressed in lysine-grown wild-type and Lys5+ transformed cells but not in Lys2+ transformed cells. A Lys2+ and Lys5+ double transformant exhibited higher alpha-aminoadipate reductase activity than lys2+ or lys5+ transformant.

Aldehyde Oxidoreductases↗

PubMed1988

Lysine biosynthesis pathway and biochemical blocks of lysine auxotrophs of Schizosaccharomyces pombe.

The alpha-aminoadipate (AA) pathway for the biosynthesis of lysine was investigated in the wild type and in lysine auxotrophs of the fission yeast Schizosaccharomyces pombe. Of the eight enzyme activities of the AA pathway that have been examined so far, six were present in the extract of wild-type S. pombe cells. Growth response to AA and accumulation studies indicated that three lysine auxotrophs, the lys2-97, lys4-95, and lys8-1 strains, were blocked before the AA step and that four lysine auxotrophs, the lys1-131, lys3-37, lys6-3, and lys7-2 strains, were blocked after the AA step. Among the mutants investigated, the lys2-97 mutant exhibited an enzyme lesion at the cis-homoaconitate hydratase step, the lys1-131 and lys7-2 mutants exhibited lesions at the AA reductase step, and lys3-37 exhibited a lesion at the saccharopine dehydrogenase step. These results demonstrated the basic similarity of the AA pathway in S. pombe and Saccharomyces cerevisiae.

2-Aminoadipic Acid↗

PubMed1987

Biosynthetic and regulatory role of lys9 mutants of Saccharomyces cerevisiae.

Derepression of lysine biosynthetic enzymes of Saccharomyces cerevisiae was investigated in lys9 auxotrophs which lack saccharopine reductase activity. Five enzymes (homocitrate synthase, homoisocitrate dehydrogenase, alpha-aminoadipate aminotransferase, alpha-aminoadipate reductase and saccharopine dehydrogenase) were constitutively derepressed in all lys9 mutants with up to eight-fold higher enzyme levels than in isogenic wild-type cells. Levels of these enzymes in lys2, lys14, and lys15 mutants were the same or lower than those in wild-type cells. The regulatory property of lys9 mutants exhibited recessiveness to the wild-type gene in heterozygous diploids. Unlike the mating type effect, homozygous diploids resulting from crosses between lys9 auxotrophs exhibited even higher levels of derepressed enzymes than the haploid mutants. Addition of a higher concentration of lysine to the growth medium resulted in reduction of enzyme levels although they were still derepressed. These results suggest that lys9 mutants represent a lesion for the saccharopine reductase and may represent a repressor mutation which in the wild-type cells simultaneously represses unlinked structural genes that encode for five of the lysine biosynthetic enzymes.

2-Aminoadipic Acid↗

PubMed1987

Purification and properties of saccharopine dehydrogenase (glutamate forming) in the Saccharomyces cerevisiae lysine biosynthetic pathway.

Saccharopine dehydrogenase (glutamate forming) of the biosynthetic pathway of lysine in Saccharomyces cerevisiae was purified 1,122-fold by using acid precipitation, ammonium sulfate precipitation, DEAE-Sepharose, gel filtration, and Reactive Red-120 agarose chromatography. The enzyme exhibited a native molecular size of 69,000 daltons by gel filtration and consisted of a single 50,000-dalton polypeptide based upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was readily denatured by exposures to temperatures exceeding 46 degrees C. The pH optimum for the reverse reaction was 9.5. The apparent Kms for L-saccharopine and NAD+ were 2.32 and 0.054 mM, respectively. The enzyme was inhibited by mercuric chloride but not by carbonyl or metal complexing agents.

Electrophoresis, Polyacrylamide Gel↗

PubMed1986

Regulation of phosphoenolpyruvate carboxykinase and pyruvate kinase in Saccharomyces cerevisiae grown in the presence of glycolytic and gluconeogenic carbon sources and the role of mitochondrial function on gluconeogenesis.

Phosphoenolpyruvate carboxykinase (PEPCKase) and pyruvate kinase (PKase) were measured in Saccharomyces cerevisiae grown in the presence of glycolytic and gluconeogenic carbon sources. The PEPCKase activity was highest in ethanol-grown cells. However, high PEPCKase activity was also observed in cells grown in 1% glucose, especially as compared with the activity of sucrose-, maltose-, or galactose-grown cells. Activity was first detected after 12 h when glucose was exhausted from the growth medium. The PKase activity was very high in glucose-grown cells; considerable activity was also present in ethanol- and pyruvate-grown cells. The absolute requirement of respiration for gluconeogenesis was demonstrated by the absence or significantly low levels of PEPCKase and fructose-1,6-bisphosphatase activities observed in respiratory deficient mutants, as well as in wild-type S. cerevisiae cells grown in the presence of glucose and antimycin A or chloramphenicol. Obligate glycolytic and gluconeogenic enzymes were present simultaneously only in stationary phase cells, but not in exponential phase cells; hence futile cycling could not occur in log phase cells regardless of the presence of carbon source in the growth medium.

Gluconeogenesis↗

PubMed1985

General and specific controls of lysine biosynthesis in Saccharomyces cerevisiae.

Six of the eight enzymes of the alpha-aminoadipate pathway for the biosynthesis of lysine in Saccharomyces cerevisiae were examined for repressibility to lysine and for susceptibility to the general control of amino acid biosynthesis. All of the enzymes exhibited a 2 to 4 fold lower level of specific activity in the wildtype strain X2180 when grown in lysine supplemented medium as compared to minimal medium. However, levels of only three of the enzymes, alpha-aminoadipate reductase, saccharopine reductase, and saccharopine dehydrogenase, were derepressed in the leaky lysine mutant 7305d and leaky arginine mutant 7853-6c when grown in minimal medium. These observations are characteristic of enzymes under general control of amino acid biosynthesis. The remaining three enzymes, homocitrate synthetase, homoaconitase and homoisocitrate dehydrogenase were repressed in 7305d cells grown in minimal or lysine supplemented medium.

Genes↗