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PubMed1998

Development of a yeast trihybrid screen using stable yeast strains and regulated protein expression.

We describe a yeast trihybrid system that facilitates rapid screening of cDNA libraries. Novel yeast vectors were developed that direct integration of cDNA encoding the bait and third protein component into the yeast chromosome. A recombinant yeast strain is thus generated (screening strain) and is available for library transformation. Transformation with the library DNA is a single, efficient transformation event, allowing the cDNA library to be represented in one step. Recovery of the library plasmid from the yeast is also simplified, since it is the only episomal plasmid. Assay of trihybrid interaction and identification of positive clones is facilitated by regulating expression of the third protein component using the yeast MET3 promoter, which is repressed in the presence of exogenous methionine. Trihybrid interactions are detected only on media lacking methionine. This trihybrid system uses the standard E. coli LacZ and yeast HIS3 reporter genes and is compatible with most available Gal4 activation domain cDNA libraries. We describe the successful application of this yeast trihybrid system to the study of phosphoprotein interactions involved in T-cell signaling.

Clone Cells↗
PubMed2000

[Development of a detection system (APC yeast color assay) of APC mutations by color change of yeast].

The author developed a sensitive yeast-based color assay which expresses APC-ADE2 (reporter) fusion protein in yeast and can screen almost the entire coding region of the APC gene. In this assay, the wild-type APC coding sequence of 8.5 kb is divided into 5 overlapping regions which are respectively ligated in-frame with an ADE2 open reading frame. The resulting five constructs containing a part of wild-type APC gene preserve the ADE2(+) phenotype (white yeast colony) when introduced into the yeast, whereas the yeast transfected with plasmids containing frameshift mutations of the APC gene shows an ADE2(-) phenotype (red yeast colony). Six human colon cancer cell lines were analyzed by this yeast color assay. HCT116 cells with wild-type APC and normal colonic mucosa gave low percentages of red colonies (0-9.9%) in all the regions. On the other hand, more than 96% red colonies were observed in one of the five regions in SW480, Colo201 and Colo320DM cells. Sequence analysis demonstrated the clonal APC mutations at codon 1,338 in SW480, 1,554 in Colo201 and 811 in Colo320DM. Moreover, the assay detected a germline mutation of the APC gene in polyps of a familial adenomatous polyposis (FAP) patient which gave about 50% red colonies. For testing the assay for clinical utilization, 18 colon cancer tissues were subjected to the assay. Eleven cancers (61%) gave more than 10% red colonies (17-57%) and clonal mutations were detected in all these samples. The same mutations were demonstrated in both DNA and RNA samples derived from idendical tissues. These results suggest that this APC yeast color assay is powerful means for detection of APC mutations in clinical samples.

Adenomatous Polyposis Coli↗
PubMed1993

Use of yeast in the study of anticancer drugs targeting DNA topoisomerases: expression of a functional recombinant human DNA topoisomerase II alpha in yeast.

A plasmid was constructed for the expression of human DNA topoisomerase II alpha in yeast from a galactose-inducible promoter of the yeast GAL1 gene. Expression of a recombinant human enzyme, in which the first 28 of the 1531 codons of human DNA topoisomerase II alpha were replaced by the first five codons of yeast DNA topoisomerase II, was shown to rescue the lethal phenotype of thermal sensitive yeast DNA topoisomerase II mutants at 35 degrees C. Purification of the human enzyme overexpressed in yeast yielded a single polypeptide with an apparent mass of 170 kDa, and the properties of the purified recombinant enzyme were found to be the same as those reported for human DNA topoisomerase II alpha purified from HeLa cells. Studies with the anticancer drug amsacrine indicated that the human enzyme, either inside yeast cells or in its purified form, is a target of the drug; inhibition of the purified enzyme by teniposide (VM-26) and merbarone was also demonstrated. These studies demonstrate that yeast strains expressing human DNA topoisomerase II alpha provide a convenient system for studying drugs targeting the enzyme; unlike mammalian systems, potential complications due to the presence of human DNA topoisomerase II beta can be eliminated in this system. Overexpression of human DNA topoisomerase II alpha in yeast also provides a convenient source of the enzyme for in vitro studies.

Antineoplastic Agents↗
PubMed1997

Fluorometric assay of binding specificity of plant lectins to yeast cells by biotin-avidin system and its application to the classification of yeast cells.

A fluorometric assay of lectin binding to yeast cells is reported. The relative amount of biotinylated lectins bound to the yeast cells was estimated by enzyme activity using 4-methylumbelliferyl-beta-D-galactoside as a substrate for the lectin-bound beta-galactosidase through biotin-avidin interaction. Binding properties of 4 mannose-specific and 3 glucose/mannose-specific lectins to 22 different species of yeast cells were studied. The binding reaction of biotinylated lectins to the yeast cells was rapid and became constant within 10 min. Each lectin showed its characteristic binding specificity to each yeast species. The relative fluorescent intensities observed for 4-methylumbelliferone released by the action of bound beta-galactosidase were good indicators for the classification of yeast cells in quantitative base. We found that the yeast cells of the Saccharomyces genus can be classified into three groups, and those of Pichia were grouped into two groups. The present method can examine many samples simultaneously and be completed within 3 h.

Agglutination↗
PubMed1996

Enumeration of bacterial and yeast colonists of apple fruits and identification of epiphytic yeasts on pear fruits in the Pacific Northwest United States.

A procedure for the isolation of diverse culturable microflora for the estimation of the population size of yeasts and bacteria on the surface of pome fruits is described. Maximum numbers of morphologically distinct colonies of both yeasts and bacteria were recovered from apple fruit surfaces when fruits were shaken for 5 min in sterile phosphate buffer plus tween, sonicated for 5 min, and aliquots of the buffer plated onto diluted yeast malt agar and diluted nutrient broth agar, respectively. The yeast and bacterial populations on the surface of unsprayed Golden Delicious apple fruits were approximately 8.0 x 10(3) and 9.5 x 10(4) colony forming units (cfu) per cm2, respectively. The densities of yeasts on the surface of pear fruits collected from Yakima, Wa, Cascade Locks, Medford, and Hood River, OR, were approximately 7.3 x 10(3), 6.4 x 10(3), 4.1 x 10(3), and 9.9 x 10(2) cfu.cm-2, respectively. The highest number of morphologically different yeast isolates were recovered from pear fruits from Cascade Locks and Hood River, Oregon and Yakima, Washington. Aureobasidium pullulans was present on fruits in all pear orchards sampled whereas Cryptococcus albidus and Rhodotorula glutinis were isolated from 80% of the orchards. Other yeasts colonizing pear fruit surfaces in 20-60% of the orchards were Cryptococcus infirmo-miniatus, Cryptococcus laurentii, Debaryomyces hansenii, Rhodotorula aurantiaca, R. fujisanensis, R. minuta and Sporobolomyces roseus.

Bacteria↗
PubMed2003

Geography and niche occupancy as determinants of yeast biodiversity: the yeast-insect-morning glory ecosystem of Kīpuka Puaulu, Hawai'i.

Biodiversity theory proposes two types of hypotheses to account for the species composition of a given community. The first encompasses geographic and historical factors. For example, local species richness is thought to be affected by area, proximity to large landmasses, dispersal mechanisms, and climatic history, collectively known as biogeography. The second type, termed niche occupancy rules, deals with the intrinsic properties of the species as they affect their interaction with the habitat and with other members of the community. The yeast-insect-morning glory ecosystem is a good model to explore biodiversity theory in ascomycetous yeasts. Here we focus on beetles that breed or feed in morning glories and a group of ascomycetous yeasts that are associated exclusively with them. Specifically, we analyse the community found in the vicinity of Kīpuka Puaulu, a small patch of disturbed but mature forest situated amidst lava flows on the island of Hawai'i. Major members of the yeast community include Metschnikowia hawaiiensis, Metschnikowia lochheadii, and the related asexual species Candida ipomoeae and Candida kipukae. These species are nearly indistinguishable from one another in terms of nutritional requirements and abilities, although their phylogenetic range is enormous. Their distribution, both global and local, is far from random. As Kīpuka Puaulu is an island within an island, the principles of island biogeography may be invoked to explain some aspects of its yeast species composition. M. lochheadii, C. ipomoeae, and the rare species Candida hawaiiana are recent introductions from the American continent and therefore exotic, whereas M. hawaiiensis and C. kipukae might be regarded as endemic, as they are yet to be isolated elsewhere. Vectoring by certain nitidulid beetles explains the long-range dispersal of these species. However, niche occupancy rules may account in part for the local spatial distribution of the yeasts within the island of Hawai'i and within the kīpuka itself. We have identified the maximum growth temperature as a potentially critical property of the fundamental niche of these yeasts.

Animals↗
PubMed1976

Thermal adaptation in yeast: growth temperatures, membrane lipid, and cytochrome composition of psychrophilic, mesophilic, and thermophilic yeasts.

The temperature limits of growth of a number of yeast species were examined, and on this basis the organisms were classified into different thermal categories. The following species were examined: Leucosporidium frigidum and Leucosporidium nivalis, psychrophilic, temperature limits of growth, -2 to 20 degrees C; Canadian lipolytica mesophilic, temperature limits of growth, 5 to 35 degrees Candida parapsilosis and Saccharomyces telluris, thermotolerant, temperature limits of growth, 8 to 42 degrees C; Torulopsis bovina and Candida slooffi, thermophilic, temperature limits of growth, 25 to 45 degrees C and 28 to 45 degrees C, respectively. The membrane lipid and cytochrome composition of mitochrondrial fractions isolated from these yeasts were compared. There was a direct correlation between the growth temperature and the degree of membrane of lipid unsaturation; the lower the temperature, the greater the degree of lipid unsaturation. The membrane lipid composition of the thermophilic yeasts were distinguished by the high percentage (30 to 40%) of saturated fatty acid, as compared with the mesophilic and psychrophilic yeasts. The latter contained approximately 90% unsaturated fatty acid, 55% of which was linolenic acid, C alpha-18:3. Changes in phospholipid composition in relation to temperature were also noted. The respiratory-deficient thermophile, C. slooffi, was characterized by the absence of cardiolipin (sensitivity 0.1 mug of phosphorus) and cytochrome aa3. The absence of conventional mitochondrial structures in this thermophilic microorganism is tentatively suggested although low concentrations of cytochromes b, c, and c1 were detected by low-temperature spectroscopy. On the other hand, the respiratory-competent thermophile, T. bovina, was characterized by a high cardiolipin (25% of the total phospholipid) and cytochrome aa3 content (1 nmol/mg of mitochrondrial protein). Low-temperature spectra showed the presence of one b-type cytochrome in the thermophilic yeasts, two b-type cytochromes in the mesophilic yeasts, and three b-type cytochromes in the psychrophilic yeasts. It was concluded that a knowledge of the properties of the biological membrane is fundamental to an understanding of the ability of a microorganism to grow and reproduce in different temperature environments.

Adaptation, Physiological↗
PubMed1981

Clinical evaluation of the AutoMicrobic system Yeast Biochemical Card for rapid identification of medically important yeasts.

The autoMicrobic system Yeast Biochemical Card (Vitek Systems, Inc., subsidiary of McDonnell Douglas, Hazelwood, Mo.), a fully automated and computer-assisted method for identifying seven yeast genera based on 26 biochemical reactions, was compared with the API 20C (Analytab Products, Plainview, N.Y) yeast identification system, using 253 clinical yeast isolates. There was an 84% correlation between the Yeast Biochemical Card and API 20C systems based on biochemical tests alone and a 96% correlation when morphology was combined with the biochemical profile. Of 22 species examined, 14 were definitively identified within 24 h, using only the biochemical tests; the remaining 8 species were presumptively identified, using biochemical tests within 24 h, with definitive identification being completed in 48 to 72 h when morphological characteristics were ascertained. The Yeast Biochemical Card system was both a facile and, with concomitant morphology, an accurate system for performing yeast identification.

Autoanalysis↗
PubMed1994

Misidentification of clinical yeast isolates by using the updated Vitek Yeast Biochemical Card.

The Vitek Yeast Biochemical Card (YBC) is widely used as a rapid identification (RI) (within 48 h) system for clinical yeast isolates. We compared the RI results obtained by the YBC technique with matched results obtained with the API 20C system. The RI of germ tube-negative yeasts isolated from 222 clinical specimens was performed with the YBC system, and the results were compared with those of standard identifications obtained by using the API 20C system and morphology, with additional biochemical reactions performed as required. Commonly isolated yeasts (Candida albicans [n = 29], Candida tropicalis [n = 40], Torulopsis [Candida] glabrata [n = 28], Candida parapsilosis [n = 12], and Cryptococcus neoformans [n = 14]) were generally well identified (115 of 123 [93%] identified correctly, with only C. albicans, C. tropicalis, and C. neoformans mis- or unidentified more than once). The RI of less commonly isolated yeasts included in the YBC database, however, was less successful (54 of 99 [55%] correct). The YBC card failed to identify 42% (10 of 24) of Candida krusei isolates, 80% (4 of 5) of Candida lambica isolates, 88% (7 of 8) of Trichosporon beigelii isolates, and 83% (10 of 12) of Cryptococcus isolates (non-C. neoformans species). For most identification failures (79%; 42 of 53) there was no identification by the end of 48 h; the other identification failures (21%; 11 of 53) gave definite but incorrect identifications. Of eight rare clinical yeast isolates not included in the Vitek database, six were correctly, not identified, while two (25%) were falsely assigned a definite RI (one Hansenula fabianii isolate was identified as Rhodotorula glutinis, and one Hansenula isolate [non-Hansenula anomala] was identified as Hansenula anomala). While the Vitek YBC rapidly and adequately identifies common yeast isolates, it fails in the RI of more unusual organisms.

Evaluation Studies as Topic↗
PubMed1996

Ability of RapID Yeast Plus System to identify 304 clinically significant yeasts within 5 hours.

The RapID Yeast Plus System (Innovative Diagnostic Systems, Norcross, Ga.) is a qualitative micromethod that uses conventional and chromogenic substrates for the identification of medically important yeasts. The ability of the RapID Yeast Plus system to accurately identify 304 clinical yeast isolates within 5 h was evaluated. The RapID Yeast Plus method correctly identified 286 (94.1%) of strains to the species level without the need for additional tests. A further 12 strains (3.9%) were classified as correct to the genus level or to a low-probability identification with two or more possibilities. In these latter cases, additional tests were required to delineate the correct identification. Organisms in the latter group comprised Candida parapsilosis (n = 1), Candida tropicalis (n = 1), Candida ciferrii (n = 1), Candida guilliermondii (n = 2), Candida humicola (n = 1), Candida kefyr (n = 1), Cryptococcus neoformans (n = 1), and Rhodotorula rubra (n = 4). Six strains (2.0%) were misidentified or did not yield codes in the manufacturer's database. These included one Candida utilis (identified as Candida famata/Candida guilliermondii), one Trichosporon beigelii (identified as Cryptococcus neoformans), one Candida diddensiae (identified as Candida albicans), one Candida membranaefaciens (identified as Candida parapsilosis), one Candida norvegensis (identified as Candida zeylanoides), and one Candida catenulata (no code) isolate; the last four strains are not included in the firm's current database. The RapID Yeast Plus system yielded excellent results and may be recommended for use in the routine laboratory for accurate same-day identification of clinically significant yeasts.

Candida↗
PubMed1992

U14 function in Saccharomyces cerevisiae can be provided by large deletion variants of yeast U14 and hybrid mouse-yeast U14 RNAs.

The functional equivalency of yeast and mouse U14 RNAs was examined in Saccharomyces cerevisiae. The test RNAs included mouse U14 and several yeast-mouse bi- and tri-partite hybrid RNAs, all transcribed from yeast U14 gene signals. The ability of the heterologous RNAs to provide essential U14 function was assessed in a test strain containing a single glucose-repressible wild-type U14 gene. Mouse U14 was not functional in yeast. However, wild-type growth was supported by hybrid RNAs that included universal sequence elements from either source, two yeast-specific segments and a 5',3' terminal stem domain. The universal sequences include box C, box D and a sequence complementary to 18S rRNA, all shown previously to be required for function of yeast U14. Deletion and substitution mapping defined the yeast-specific elements and showed that a major portion of neighboring non-conserved RNA is dispensible. The results are discussed with a view to defining a minimal consensus U14 molecule.

Animals↗
PubMed2001

Yeast-Yeast Interactions in Guava and Tomato Fruits.

The host specificity of yeast-yeast interactions was investigated for two yeast types, represented by six pairs of Pichia membranifaciens clade yeasts (Pichia membranifaciens or Issatchenkia occidentalis) with apiculate yeasts (Kloeckera apis, Kloeckera africana, or Saccharomycodes ludwigii), commonly found in fruits. Competitive interactions between the two types were detected in both ripe tomato and guava fruit pulp. The differences in growth rates and carrying capacities depended on fruit type (host) and culture conditions (monocultures versus bicultures). These differences were probably due to nutrient composition of each fruit. Pichia membranifaciens did not show host dependent responses, but the apiculate yeasts and Issatchenkia occidentalis did. Depending on yeast strain and culture conditions (i.e., monoculture or biculture), carbon, nitrogen, and vitamins were investigated as potential limiting growth factors in guava fruit. Both singular and multiple limiting nutrients were implicated.

Journal Article↗
PubMed1988

Cloning and analysis of a yeast genomic DNA sequence capable of directing gene transcription in Escherichia coli as well as in yeast.

A DNA fragment was isolated from yeast genomic sequences by its ability to direct the transcription of promoterless CmR (cat) gene in Escherichia coli and in yeast. Nucleotide sequencing and primer extension analysis showed that yeast DNA contains sets of consensus sequences pertaining to prokaryotic and yeast-type promoter elements. It was designated as yeast- and E. coli-type promoter (YEP1). Typical E. coli-type promoter elements are found at appropriate positions: TATTTT from -12 to -7 and TTGTCC from -35 to -30 with their spacing of 17 bp from the single mRNA start point determined by the primer extension. Analysis of cat transcripts from yeast cells showed that the YEP1 caused multiple transcription initiations at more than 20 different points that are spaced over a 100-bp region. The DNA is composed of A + T-rich sequences and putative TATA-like sequences are found at several places upstream from the transcription start points. Deletion analysis showed that a 276-bp sequence between -872 and -596 from the initiating ATG codon was required for the maximal promoter activity in yeast but not in E. coli.

Base Sequence↗
PubMed2006

Mitochondrial import of human and yeast fumarase in live mammalian cells: retrograde translocation of the yeast enzyme is mainly caused by its poor targeting sequence.

Studies on yeast fumarase provide the main evidence for dual localization of a protein in mitochondria and cytosol by means of retrograde translocation. We have examined the subcellular targeting of yeast and human fumarase in live cells to identify factors responsible for this. The cDNAs for mature yeast or human fumarase were fused to the gene for enhanced green fluorescent protein (eGFP) and they contained, at their N-terminus, a mitochondrial targeting sequence (MTS) derived from either yeast fumarase, human fumarase, or cytochrome c oxidase subunit VIII (COX) protein. Two nuclear localization sequences (2x NLS) were also added to these constructs to facilitate detection of any cytosolic protein by its targeting to nucleus. In Cos-1 cells transfected with these constructs, human fumarase with either the native or COX MTSs was detected exclusively in mitochondria in >98% of the cells, while the remainder 1-2% of the cells showed varying amounts of nuclear labeling. In contrast, when human fumarase was fused to the yeast MTS, >50% of the cells showed nuclear labeling. Similar studies with yeast fumarase showed that with its native MTS, nuclear labeling was seen in 80-85% of the cells, but upon fusion to either human or COX MTS, nuclear labeling was observed in only 10-15% of the cells. These results provide evidence that extramitochondrial presence of yeast fumarase is mainly caused by the poor mitochondrial targeting characteristics of its MTS (but also affected by its primary sequence), and that the retrograde translocation mechanism does not play a significant role in the extramitochondrial presence of mammalian fumarase.

Animals↗
PubMed2006

Interactions between yeast lees and wine polyphenols during simulation of wine aging. II. Analysis of desorbed polyphenol compounds from yeast lees.

In the first part of this work, the analysis of the polyphenolic compounds remaining in the wine after different contact times with yeast lees during simulation of red wine aging was undertaken. To achieve a more precise view of the wine polyphenols adsorbed on lees during red wine aging and to establish a clear balance between adsorbed and remnant polyphenol compounds, the specific analysis of the chemical composition of the adsorbed polyphenolic compounds (condensed tannins and anthocyanins) after their partial desorbtion from yeast lees by denaturation treatments was realized in the second part of the study. The total recovery of polyphenol compounds from yeast lees was not complete, since a rather important part of the initial wine colored polyphenols, especially those with a dominant blue color component, remained strongly adsorbed on yeast lees, as monitored by color tristimulus and reflectance spectra measurements. All anthocyanins were recovered at a rather high percentage (about 62%), and it was demonstrated that they were not adsorbed in relation with their sole polarity. Very few monomeric phenolic compounds were extracted from yeast lees. With the use of drastic denaturing treatments, the total recovery of condensed tannins reached 83%. Such tannins extracted from yeast lees exhibited very high polymeric size and a rather high percentage of galloylated residues by comparison with initial wine tannins, indicating that nonpolar tannins were preferentially desorbed from yeast lees by the extraction treatments.

Adsorption↗
PubMed1997

Seasonal occurrence of yeasts and yeast-like organisms in the river Danube.

One hundred and seventy yeast strains belonging to 14 genera and 29 species were isolated from 112 water samples of the river Danube in the area of Bratislava. The samples were collected through the year from April to March. Saccharomyces cerevisiae, Candida maltosa, Aureobasidium pullulans, Cystofilobasidium capitatum, Rhodotorula glutinis, Geotrichum candidum, and Candida krusei were the most frequent. The basidiomycetous yeasts and yeast-like organisms with oxidative metabolism were present in approximately equal numbers to those with fermentative metabolism. Saccharomyces cerevisiae was the dominant yeast and was isolated from 50% of all samples examined and represented approximately one quarter of the yeast community. Yeast densities ranged from 100 to 21,100 CFU per litre. The highest population density was observed in October. Cryptococcus albidus, Saccharomyces cerevisiae, Rhodotorula glutinis, and Aureobasidium pullulans formed the main part of the yeast population in this month.

Aerobiosis↗
PubMed2000

A new method for yeast recovery in batch ethanol fermentations: filter aid filtration followed by separation of yeast from filter aid using hydrocyclones.

In the Melle-Boinot process for alcohol production, centrifuges are normally used for yeast recovery at the end of a batch fermentation. Centrifuges are expensive equipment and represent an impressive part of the equipment costs in alcohol industries. In the present work, an alternative method for yeast recovery using less expensive equipment was studied. Instead of using centrifuges, yeast was separated from the fermented broth by filter aid filtration, followed by separation of yeast from the filter aid using hydrocyclones. A stainless steel plate-and-frame filter of filtration area 1.14 m2 and two 30 mm hydrocyclones, which followed the Bradley and Rietema recommended proportions, were used in this work. The filter aid was perlite. Tests of direct separation of yeast from the fermented broth using the Bradley hydrocyclone proved to be completely unfeasible, since the maximal reduced total efficiency obtained was only 1%. When the hydrocyclones were used to separate perlite from the resuspended filtration cake, the perlite total separation efficiency obtained in the underflow was as high as 95% when using the Bradley hydrocyclone with an underflow diameter of 3 mm. To show the feasibility of the proposed new method of yeast recovery, a complete cycle of experiments, which included fermentation, yeast separation, and new fermentation using the recycled cells, was performed with good results.

Centrifugation↗
PubMed1979

Evidence for transcriptional regulation of orotidine-5'-phosphate decarboxylase in yeast by hybridization of mRNA to the yeast structural gene cloned in Escherichia coli.

From a large population of strains of Escherichia coli carrying shear fragments of yeast (Saccharomyces cerevisiae) DNA attached by in vitro recombination to the plasmid vector pMB9, two hybrid plasmids were selected that relieve the pyrimidine requirement of nonreverting pyrF mutants of E. coli. An 1100-base-pair DNA fragment common to the two complementing plasmids was recloned into another plasmid vector, pBR322; these new hybrids retained the ability to specify orotidine-5'-phosphate decarboxylase (orotidine-5'-phosphate carboxy-lyase, EC 4.1.1.23) synthesis in E. coli. Evidence is presented that this common fragment is yeast DNA and thus apparently carried the structural information for yeast orotidine-5'-phosphate decarboxylase, the product of yeast gene ura3. A hybrid plasmid containing the 1100-base-pair fragment was used to measure levels of putative ura3 mRNA from yeast cultures labeled with [3H]adenine, ura3 mRNA was unstable with an apparent half-life of 10.5 min. Under different circumstances previously shown to alter the level of orotidine-5'-phosphate decarboxylase in yeast, a coordinate variation in proportion of labeled RNA complementary to the hybrid plasmid was found. These data support the hypothesis that regulation of the ura3 gene in yeast is at the level of transcription.

Carboxy-Lyases↗