The ASP1 gene of Saccharomyces cerevisiae, encoding the intracellular isozyme of L-asparaginase

Optimizing recombinant production of L-asparaginase 1 from Saccharomyces cerevisiae using response surface methodology

L-asparaginase is an essential enzyme used in cancer treatment, but its production faces challenges like low yield, high cost, and immunogenicity. Recombinant production is a promising method to overcome these limitations. In this study, response surface methodology (RSM) was used to optimize the production of L-asparaginase 1 from Saccharomyces cerevisiae in Escherichia coli K-12 BW25113. The Box-Behnken design (BBD) was utilized for the RSM modeling, and a total of 29 experiments were conducted. These experiments aimed to examine the impact of different factors, including the concentration of isopropyl-b-LD-thiogalactopyranoside (IPTG), the cell density prior to induction, the duration of induction, and the temperature, on the expression level of L-asparaginase 1. The results revealed that while the post-induction temperature, cell density at induction time, and post-induction time all had a significant influence on the response, the post-induction time exhibited the greatest effect. The optimized conditions (induction at cell density 0.8 with 0.7 mM IPTG for 4 h at 30 °C) resulted in a significant amount of L-asparaginase with a titer of 93.52 μg/mL, which was consistent with the model-based prediction. The study concluded that RSM optimization effectively increased the production of L-asparaginase 1 in E. coli, which could have the potential for large-scale fermentation. Further research can explore using other host cells, optimizing the fermentation process, and examining the effect of other variables to increase production.

Mosaic Genome of a British Cider Yeast

Hybrid formation and introgressions had a profound impact on fermentative yeasts domesticated for beer, wine and cider fermentations. Here we provide a comparative genomic analysis of a British cider yeast isolate (E1) and characterize its fermentation properties. E1 has a Saccharomyces uvarum genome into which ~102 kb of S. eubayanus DNA were introgressed that replaced the endogenous homologous 55 genes of chromosome XIV between YNL182C and YNL239W. Sequence analyses indicated that the DNA donor was either a lager yeast or a yet unidentified S. eubayanus ancestor. Interestingly, a second introgression event added ~66 kb of DNA from Torulaspora microellipsoides to the left telomere of SuCHRX. This region bears high similarity with the previously described region C introgression in the wine yeast EC1118. Within this region FOT1 and FOT2 encode two oligopeptide transporters that promote improved nitrogen uptake from grape must in E1, as was reported for EC1118. Comparative laboratory scale grape must fermentations between the E1 and EC1118 indicated beneficial traits of faster consumption of total sugars and higher glycerol production but low acetic acid and reduced ethanol content. Importantly, the cider yeast strain produced high levels of fruity ester, including phenylethyl and isoamyl acetate.

Anticancer Activity of Extremely Effective Recombinant L-Asparaginase from Burkholderia pseudomallei

L-asparaginase (E.C. 3.5.1.1) purified from bacterial cells is widely used in the food industry, as well as in the treatment of childhood acute lymphoblastic leukemia. In the present study, the Burkholderia pseudomallei L-asparaginase gene was cloned into the pGEX-2T DNA plasmid, expressed in E. coli BL21 (DE3) pLysS, and purified to homogeneity using Glutathione Sepharose chromatography with 7.26 purification fold and 16.01% recovery. The purified enzyme exhibited a molecular weight of ~33.6 kDa with SDS-PAGE and showed maximal activity at 50°C and pH 8.0. It retained 95.1, 89.6%, and 70.2% initial activity after 60 min at 30°C, 40°C, and 50°C, respectively. The enzyme reserved its activity at 30°C and 37°C up to 24 h. The enzyme had optimum pH of 8 and reserved 50% activity up to 24 h. The recombinant enzyme showed the highest substrate specificity towards L-asparaginase substrate, while no detectable specificity was observed for L-glutamine, urea, and acrylamide at 10 mM concentration. THP-1, a human leukemia cell line, displayed significant morphological alterations after being treated with recombinant L-asparaginase and the IC₅₀ of the purified enzyme was recorded as 0.8 IU. Furthermore, the purified recombinant L-asparaginase improved cytotoxicity in liver cancer HepG2 and breast cancer MCF-7 cell lines, with IC₅₀ values of 1.53 and 18 IU, respectively.

Autophagy sustains glutamate and aspartate synthesis in Saccharomyces cerevisiae during nitrogen starvation

Autophagy catabolizes cellular constituents to promote survival during nutrient deprivation. Yet, a metabolic comprehension of this recycling operation, despite its crucial importance, remains incomplete. Here, we uncover a specific metabolic function of autophagy that exquisitely adjusts cellular metabolism according to nitrogen availability in the budding yeast Saccharomyces cerevisiae. Autophagy enables metabolic plasticity to promote glutamate and aspartate synthesis, which empowers nitrogen-starved cells to replenish their nitrogen currency and sustain macromolecule synthesis. Our findings provide critical insights into the metabolic basis by which autophagy recycles cellular components and may also have important implications in understanding the role of autophagy in diseases such as cancer.

The l-Thr Kinase/l-Thr-Phosphate Decarboxylase (CobD) Enzyme from Methanosarcina mazei Gö1 Contains Metallocenters Needed for Optimal Activity

The MM2060 (cobD) gene from Methanosarcina mazei strain Gö1 encodes a protein (MmCobD) with l-threonine kinase (PduX) and l-threonine-O-3-phosphate decarboxylase (CobD) activities. In addition to the unexpected l-Thr kinase activity, MmCobD has an extended carboxy-terminal (C-terminal) region annotated as a putative metal-binding zinc finger-like domain. Here, we demonstrate that the C-terminus of MmCobD is a ferroprotein containing ∼25 non-heme iron atoms per monomer of protein. The absence of the C-terminus substantially reduces, but does not abolish, enzymatic activities in vitro and in vivo. Single-residue substitutions of C-terminal putative Fe-binding cysteinyl and histidinyl residues resulted in the loss of Fe and changes in enzyme activity levels. Salmonella enterica ΔpduX and ΔcobD strains were used as heterologous hosts to assess coenzyme B12 biosynthesis as a function of 17 MmCobD variants tested. Some of the latter displayed 5-fold higher enzymatic activity in vitro and enhanced the growth rate of the S. enterica strains that synthesized them. Most of the MmCobD variants tested were up to 6-fold less active in vitro and supported slow growth rates of the S. enterica strains that synthesized them; some substitutions abolished enzyme activity. MmCobD exhibited an ultraviolet-visible absorption spectrum consistent with [4Fe-4S] clusters that appeared to be susceptible to oxidation by H2O2 and reduction by sodium dithionite. The presence of FeS clusters in MmCobD was corroborated by electron paramagnetic resonance and magnetic circular dichroism studies. Collectively, our results suggest that MmCobD contains one or more diamagnetic [4Fe-4S]2+ center(s) that may play a structural or regulatory role.

Recombinant L-asparaginase 1 from Saccharomyces cerevisiae: an allosteric enzyme with antineoplastic activity

L-asparaginase (L-ASNase) (EC 3.5.1.1) is an important enzyme for the treatment of acute lymphoblastic leukaemia. Currently, the enzyme is obtained from bacteria, Escherichia coli and Erwinia chrysanthemi. The bacterial enzymes family is subdivided in type I and type II; nevertheless, only type II have been employed in therapeutic proceedings. However, bacterial enzymes are susceptible to induce immune responses, leading to a high incidence of adverse effects compromising the effectiveness of the treatment. Therefore, alternative sources of L-ASNase may be useful to reduce toxicity and enhance efficacy. The yeast Saccharomyces cerevisiae has the ASP1 gene responsible for encoding L-asparaginase 1 (ScASNase1), an enzyme predicted as type II, like bacterial therapeutic isoforms, but it has been poorly studied. Here we characterised ScASNase1 using a recombinant enzyme purified by affinity chromatography. ScASNase1 has specific activity of 196.2 U/mg and allosteric behaviour, like type I enzymes, but with a low K_0.5 = 75 μM like therapeutic type II. We showed through site-directed mutagenesis that the T64-Y78-T141-K215 residues are involved in catalysis. Furthermore, ScASNase1 showed cytotoxicity for the MOLT-4 leukemic cell lineage. Our data show that ScASNase1 has characteristics described for the two subfamilies of l-asparaginase, types I and II, and may have promising antineoplastic properties.

Inferring gene family histories in yeast identifies lineage specific expansions

The complement of genes found in the genome is a balance between gene gain and gene loss. Knowledge of the specific genes that are gained and lost over evolutionary time allows an understanding of the evolution of biological functions. Here we use new evolutionary models to infer gene family histories across complete yeast genomes; these models allow us to estimate the relative genome-wide rates of gene birth, death, innovation and extinction (loss of an entire family) for the first time. We show that the rates of gene family evolution vary both between gene families and between species. We are also able to identify those families that have experienced rapid lineage specific expansion/contraction and show that these families are enriched for specific functions. Moreover, we find that families with specific functions are repeatedly expanded in multiple species, suggesting the presence of common adaptations and that these family expansions/contractions are not random. Additionally, we identify potential specialisations, unique to specific species, in the functions of lineage specific expanded families. These results suggest that an important mechanism in the evolution of genome content is the presence of lineage-specific gene family changes.

Nitrogen regulation involved in the accumulation of urea in Saccharomyces cerevisiae

Rice wine is a popular traditional alcoholic drink with a long history in China. However, the presence of the potential carcinogen ethyl carbamate (EC) raises a series of food safety concerns. Although the metabolic pathway of urea (the major precusor of EC) has been characterized in Saccharomyces cerevisiae, the regulation of urea accumulation remains unclear, making the efficient elimination of urea difficult. To demonstrate the regulatory mechanisms governing urea accumulation, three key nitrogen sources that can inhibit urea utilization for a commercial S. cerevisiae strain were identified. In addition, regulators of nitrogen catabolite repression (NCR) and target of rapamycin (TOR) pathways were identified as being involved in urea accumulation by real-time quantitative PCR. Based on these results, preferred nitrogen sources were found to repress urea utilization by converting them to glutamine or glutamate. Moreover, the results indicated that the manner of urea metabolism regulation was different for two positive regulators involved in NCR; Gln3p can be retained in the cytoplasm by glutamine, while Gat1p can be retained by glutamine and glutamate. Furthermore, this was confirmed by fluorescence location detection. These new findings provide new targets for eliminating EC and other harmful nitrogen-containing compounds in fermented foods.

The ASP3 locus in Saccharomyces cerevisiae originated by horizontal gene transfer from Wickerhamomyces

The asparagine degradation pathway in the S288c laboratory strain of Saccharomyces cerevisiae is comprised of genes located at two separate loci. ASP1 is located on chromosome IV and encodes for cytosolic l-asparaginase I, whereas ASP3 contains a gene cluster located on chromosome XII comprised of four identical genes, ASP3-1, ASP3-2, ASP3-3, and ASP3-4, which encode for cell wall-associated l-asparaginase II. Interestingly, the ASP3 locus appears to be only present, in variable copy number, in S. cerevisiae strains isolated from laboratory or industrial environments and is completely absent from the genomes of 128 diverse fungal species. Investigation of the evolutionary history of ASP3 across these 128 genomes as well as across the genomes of 43 S. cerevisiae strains shows that ASP3 likely arose in a S. cerevisiae strain via horizontal gene transfer (HGT) from, or a close relative of, the wine yeast Wickerhamomyces anomalus, which co-occurs with S. cerevisiae in several biotechnological processes. Thus, because the ASP3 present in the S288c laboratory strain of S. cerevisiae is induced in response to nitrogen starvation, its acquisition may have aided yeast adaptation to artificial environments. Our finding that the ASP3 locus in S. cerevisiae originated via HGT further highlights the importance of gene sharing between yeasts in the evolution of their remarkable metabolic diversity.

Transcriptional responses ofSaccharomyces cerevisiaeto preferred and nonpreferred nitrogen sources in glucose-limited chemostat cultures

Aerobic, glucose-limited chemostat cultures of Saccharomyces cerevisiae grown with six different nitrogen sources were subjected to transcriptome analysis. The use of chemostats enabled an analysis of nitrogen-source-dependent transcriptional regulation at a fixed specific growth rate. A selection of preferred (ammonium and asparagine) and nonpreferred (leucine, phenylalanine, methionine and proline) nitrogen sources was investigated. For each nitrogen source, distinct sets of genes were induced or repressed relative to the other five nitrogen sources. In total, 131 such 'signature transcripts' were identified in this study. In addition to signature transcripts, genes were identified that showed a transcriptional coresponse to two or more of the six nitrogen sources. For example, 33 genes were transcriptionally upregulated in leucine-grown, phenylalanine-grown and methionine-grown cultures; this was partly attributed to the involvement of common enzymes in the dissimilation of these amino acids. In addition to specific transcriptional responses elicited by individual nitrogen sources, their impact on global regulatory mechanisms such as nitrogen catabolite repression (NCR) were monitored. NCR-sensitive gene expression in the chemostat cultures showed that ammonium and asparagine were 'rich' nitrogen sources. By this criterion, leucine, proline and methionine were 'poor' nitrogen sources, and phenylalanine showed an 'intermediate' NCR response.

Single QTL mapping and nucleotide-level resolution of a physiologic trait in wine Saccharomyces cerevisiae strains

Natural Saccharomyces cerevisiae yeast strains exhibit very large genotypic and phenotypic diversity. However, the link between phenotype variation and genetic determinism is still difficult to identify, especially in wild populations. Using genome hybridization on DNA microarrays, it is now possible to identify single-feature polymorphisms among divergent yeast strains. This tool offers the possibility of applying quantitative genetics to wild yeast strains. In this instance, we studied the genetic basis for variations in acetic acid production using progeny derived from two strains from grape must isolates. The trait was quantified during alcoholic fermentation of the two strains and 108 segregants derived from their crossing. A genetic map of 2212 markers was generated using oligonucleotide microarrays, and a major quantitative trait locus (QTL) was mapped with high significance. Further investigations showed that this QTL was due to a nonsynonymous single-nucleotide polymorphism that targeted the catalytic core of asparaginase type I (ASP1) and abolished its activity. This QTL was only effective when asparagine was used as a major nitrogen source. Our results link nitrogen assimilation and CO(2) production rate to acetic acid production, as well as, on a broader scale, illustrating the specific problem of quantitative genetics when working with nonlaboratory microorganisms.

Characterization of cell wall associated proteins of a Staphylococcus aureus isolated from bovine mastitis case by a proteomic approach

Staphylococcus aureus causes different pathologies in humans and animals. In particular, it is involved in intramammary infections in cows, causing economic losses and milk-safety problems. Although it is well-known that surface components (proteins and capsular polysaccharides) and exotoxins are virulence factors involved in the pathogenesis of bovine mastitis, less is known about the precise biochemical identity of such molecules. Therefore, mapping of surface proteins using specific disease- and environment-isolates provides a benchmark for strain comparison of pathogens with different pathogenic characteristics and antibiotic resistance mechanism and can aid in defining specific vaccine and therapeutic targets. In this study, we used a proteomic approach on protein extracts of lysostaphin-treated S. aureus in isotonic conditions, to produce a reproducible and well resolved 2-D electrophoresis (2-DE) reference map of surface associated proteins of isolated S. aureus from a case of bovine mastitis. The most abundant protein components were identified by Matrix assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry.

Nitrogen regulation in Saccharomyces cerevisiae

Yeast cells can respond to growth on relatively poor nitrogen sources by increasing expression of the enzymes for the synthesis of glutamate and glutamine and by increasing the activities of permeases responsible for the uptake of amino acids for use as a source of nitrogen. These general responses to the quality of nitrogen source in the growth medium are collectively termed nitrogen regulation. In this review, we discuss the historical foundations of the study of nitrogen regulation as well as the current understanding of the regulatory networks that underlie nitrogen regulation. One focus of the review is the array of four GATA type transcription factors which are responsible for the regulation the expression of nitrogen-regulated genes. They are the activators Gln3p and Nil1p and their antagonists Nil2p and Dal80p. Our discussion includes consideration of the DNA elements which are the targets of the transcription factors and of the regulated translocation of Gln3p and Nil1p from the cytoplasm to the nucleus. A second focus of the review is the nitrogen regulation of the general amino acid permease, Gap1p, and the proline permease, Put4p, by ubiquitin mediated intracellular protein sorting in the secretory and endosomal pathways.

The role of ammonia metabolism in nitrogen catabolite repression in Saccharomyces cerevisiae

Saccharomyces cerevisiae is able to use a wide variety of nitrogen sources for growth. Not all nitrogen sources support growth equally well. In order to select the best out of a large diversity of available nitrogen sources, the yeast has developed molecular mechanisms. These mechanisms consist of a sensing mechanism and a regulatory mechanism which includes induction of needed systems, and repression of systems that are not beneficial. The first step in use of most nitrogen sources is its uptake via more or less specific permeases. Hence the first level of regulation is encountered at this level. The next step is the degradation of the nitrogen source to useful building blocks via the nitrogen metabolic pathways. These pathways can be divided into routes that lead to the degradation of the nitrogen source to ammonia and glutamate, and routes that lead to the synthesis of nitrogen containing compounds in which glutamate and glutamine are used as nitrogen donor. Glutamine is synthesized out of ammonia and glutamate. The expression of the specific degradation routes is also regulated depending on the availability of a particular nitrogen source. Ammonia plays a central role as intermediate between degradative and biosynthetic pathways. It not only functions as a metabolite in metabolic reactions but is also involved in regulation of metabolic pathways at several levels. This review describes the central role of ammonia in nitrogen metabolism. This role is illustrated at the level of enzyme activity, translation and transcription.

Cloning and expression of cDNA encoding rat liver 60-kDa lysophospholipase containing an asparaginase-like region and ankyrin repeat

Mammalian tissues contain small form and large form lysophospholipases. Here we report the cloning, sequence, and expression of cDNA encoding the latter form of lysophospholipase using antibody raised against the enzyme purified from rat liver supernatant (Sugimoto, H., and Yamashita, S. (1994) J. Biol. Chem. 269, 6252-6258). The 2,539-base pair cDNA encoded 564 amino acid residues with a calculated Mr of 60,794. The amino-terminal two-thirds of the deduced amino acid sequence significantly resembled Escherichia coli asparaginase I with the putative asparaginase catalytic triad Thr-Asp-Lys and was followed by leucine zipper motif. The carboxyl-terminal region carried ankyrin repeat. When the cDNA was transfected into HEK293 cells, not only lysophospholipase activity but also asparaginase and platelet-activating factor acetylhydrolase activities were expressed. Reverse transcription-polymerase chain reaction revealed that the transcript occurred at high levels in liver and kidney but was hardly detectable in lung and heart from which large form lysophospholipases had been purified, suggesting the presence of multiple forms of large form lysophospholipase in mammalian tissues.

Human glucokinase regulatory protein (GCKR): cDNA and genomic cloning, complete primary structure, and chromosomal localization

Null mutations in the glucokinase (GCK) gene can cause autosomal dominant type 2 diabetes (maturity onset diabetes of the young, MODY); however, MODY is genetically heterogeneous. In both liver and pancreatic islet, glucokinase is subject to inhibition by a regulatory protein (GCKR). Given the role of GCK in MODY, GCKR is itself a candidate type 2 diabetes susceptibility gene. Here we describe the structure of full-length (2.2 kb) cDNA for human GCKR, from the hepatoblastoma cell line HepG2. The human GCKR translation product has 625 amino acids and a predicted molecular weight of 68,700. It has 88% amino acid identity to rat GCKR. Yeast artificial chromosomes (YAC clones) containing human GCKR were isolated, and the gene was mapped to Chromosome (Chr) 2p23 by fluorescent in situ hybridization and somatic cell hybrid analysis.