The combined effects of temperature and dilution on the activity and feedback inhibition of yeast aspartate transcarbamylase

1969 ◽  
Vol 47 (4) ◽  
pp. 477-479 ◽  
Author(s):  
J. G. Kaplan ◽  
Irmgard Messmer
Keyword(s):  
Low Temperature ◽  
Sharp Increase ◽  
Specific Activity ◽  
Feedback Inhibition ◽  
Combined Effects ◽  
Regulatory Site ◽  
Aspartate Transcarbamylase ◽  
Small Loss ◽  
Progressive Loss ◽  
Effects Of Temperature

Dilution of a partially purified preparation of yeast aspartate transcarbamylase caused only a small loss of feedback inhibition and no change in specific activity when the assay was carried out at low temperature (0–10 °C). As the temperature of assay was increased, there was in the case of the dilute preparation a progressive loss of feedback inhibition coupled with a sharp increase in specific activity, reaching a level 400–500% that of the concentrated preparations. The data suggest that this is due to a dissociation into subunits possessing high aspartate transcarbamylase activity but lacking the regulatory site.

Aggregation States of a Regulatory Enzyme Complex Catalyzing the Early Steps of Pyrimidine Biosynthesis in Bakers' Yeast

1971 ◽  
Vol 49 (4) ◽  
pp. 403-411 ◽  
Author(s):  
P. F. Lue ◽  
J. G. Kaplan
Keyword(s):  
Molecular Weight ◽  
Density Gradient ◽  
Crude Extract ◽  
Analytical Ultracentrifugation ◽  
Specific Activity ◽  
Feedback Inhibition ◽  
Gradient Centrifugation ◽  
Sucrose Density Gradient ◽  
Regulatory Site ◽  
Aspartate Transcarbamylase

Aspartate transcarbamylase (ATCase) of bakers' yeast has been purified 78-fold from a crude extract of a derepressed diploid strain; its specific activity was more than 300-fold that of a wild-type crude extract. During the last steps of the purification there was a parallel co-purification of carbamylphosphate synthetase (CPSase), and both activities retained full sensitivity to feedback inhibition by UTP; indeed the sensitivity of the ATCase to UTP increased during the purification doubtless due to discard of a feedback-insensitive ATCase subunit. The two enzyme activities co-eluted from gel filtration on Sepharose 6B together with the feedback site. Analytical ultracentrifugation revealed that the material was not homogeneous, showing two major peaks. Sucrose density gradient centrifugation in the presence of UTP, glutamine, and Mg2+ resulted in co-sedimentation of the two activities and the regulatory site, corresponding to a molecular weight of approximately 800 000 daltons. Omission of UTP from the gradient resulted in disappearance of the heavy peak and appearance of a new one, corresponding to a molecular weight of 380 000 and possessing both activities; the CPSase was still highly sensitive to UTP unlike the ATCase which was only slightly sensitive to retroinhibition. Omission of glutamine and Mg2+ from the sucrose density gradient caused a distinct CPSase peak to trail behind the ATCase; again, the CPSase (molecular weight 250 000) retained full sensitivity to feedback inhibition. This, together with genetic data, supports the view that the ura-2 gene which controls ATCase, CPSase, and the regulatory site is a polycistronic operon, coding for the production of two or three polypeptide chains; the CPSase subunit is inactive unless a regulatory site is present, whereas the ATCase subunit (molecular weight 140 000) is highly active but completely insensitive to feedback inhibition.

The combined effects of temperature, leaf wetness, and inoculum concentration on infection of cucumbers with Pseudoperonospora cubensis

1977 ◽  
Vol 55 (11) ◽  
pp. 1478-1487 ◽  
Author(s):  
Yigal Cohen
Keyword(s):  
Sharp Increase ◽  
Factorial Experiment ◽  
The Other ◽  
Leaf Wetness ◽  
Pseudoperonospora Cubensis ◽  
Disease Development ◽  
Combined Effects ◽  
Single Treatment ◽  
Inoculum Concentration ◽  
Effects Of Temperature

The infection of susceptible cucumber leaves by Pseudoperonospora cubensis was investigated under controlled conditions in a 6 × 3 × 4 factorial experiment with 72 combinations of temperature, inoculum concentration, and leaf-wetness duration. The minimum, maximum, and optimum levels of each factor for symptom production were found to depend on one or both of the other factors. The minimal temperature for infection was 20 °C with 2 h of wetness and this decreased to 10–15 and 5–10 °C with 6 and 12 h of wetness, respectively, according to the inoculum load. The maximal temperature for infection was 25 °C, except for a single treatment in which some infection occurred at 28 °C. Optimal temperatures for infection were 20, 15–20, 10–20, and 5–20 °C at dew periods of 2, 6, 12, and 24 h, respectively. The shortest dew period needed to establish infection was 2 h. A sharp increase in infection was associated with extending the dew period to 6h. Further lengthening of the dew period resulted in more infection under unfavorable combinations of temperature and inoculum concentration. An inoculum load of 10 sporangia/cm2 was minimal for infection under favorable combinations of temperature and wetness, and higher loads were needed under unfavorable combinations. The optimal inoculum concentration was 1000 sporangia/cm2 under most inoculation circumstances. The implications of the variable behaviour of the pathogen to disease development in the field are discussed.

scholarly journals Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus

Toxins ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 425
Author(s):  
Yunyu Tang ◽  
Haiyan Zhang ◽  
Yu Wang ◽  
Chengqi Fan ◽  
Xiaosheng Shen
Keyword(s):  
Tissue Distribution ◽  
Combined Effects ◽  
Mytilus Coruscus ◽  
Paralytic Shellfish Toxins ◽  
Rapid Elimination ◽  
Simulated Environment ◽  
Paralytic Shellfish ◽  
Algal Abundance ◽  
Effects Of Temperature ◽  
The Impact

This study assessed the impact of increasing seawater surface temperature (SST) and toxic algal abundance (TAA) on the accumulation, tissue distribution and elimination dynamics of paralytic shellfish toxins (PSTs) in mussels. Mytilus coruscus were fed with the PSTs-producing dinoflagellate A. catenella under four simulated environment conditions. The maximum PSTs concentration was determined to be 3548 µg STX eq.kg−1, which was four times higher than the EU regulatory limit. The increasing SST caused a significant decline in PSTs levels in mussels with rapid elimination rates, whereas high TAA increased the PSTs concentration. As a result, the PSTs toxicity levels decreased under the combined condition. Additionally, toxin burdens were assessed within shellfish tissues, with the highest levels quantified in the hepatopancreas. It is noteworthy that the toxin burden shifted towards the mantle from gill, muscle and gonad at the 17th day. Moreover, variability of PSTs was measured, and was associated with changes in each environmental factor. Hence, this study primarily illustrates the combined effects of SST and TAA on PSTs toxicity, showing that increasing environmental temperature is of benefit to lower PSTs toxicity with rapid elimination rates.

Combined effects of temperature and diet on growth and biochemical composition of the Pacific oyster Crassostrea gigas (Thunberg) spat

2004 ◽  
Vol 35 (12) ◽  
pp. 1131-1140 ◽  
Author(s):  
Cecilia Flores-Vergara ◽  
Beatriz Cordero-Esquivel ◽  
Ana Nallely Ceron-Ortiz ◽  
Bertha O Arredondo-Vega
Keyword(s):  
Crassostrea Gigas ◽  
Biochemical Composition ◽  
Pacific Oyster ◽  
Combined Effects ◽  
The Pacific ◽  
Effects Of Temperature

Combined effects of aging and low temperature, long time heating on pork toughness

Meat Science ◽  
2019 ◽  
Vol 150 ◽  
pp. 33-39 ◽  
Author(s):  
Shengjie Li ◽  
Renchao Ma ◽  
Jinfeng Pan ◽  
Xinping Lin ◽  
Xiuping Dong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Combined Effects ◽  
Long Time ◽  
Effects Of Aging

Combined Effects of Temperature and Velocity Jump on the Heat Transfer, Fluid Flow, and Entropy Generation Over a Single Rotating Disk

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
A. Arikoglu ◽  
G. Komurgoz ◽  
I. Ozkol ◽  
A. Y. Gunes
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Entropy Generation ◽  
Rotating Disk ◽  
Heat Transfer Fluid ◽  
Combined Effects ◽  
Jump Conditions ◽  
Governing Equations ◽  
Velocity Jump ◽  
Effects Of Temperature

The present work examines the effects of temperature and velocity jump conditions on heat transfer, fluid flow, and entropy generation. As the physical model, the axially symmetrical steady flow of a Newtonian ambient fluid over a single rotating disk is chosen. The related nonlinear governing equations for flow and thermal fields are reduced to ordinary differential equations by applying so-called classical approach, which was first introduced by von Karman. Instead of a numerical method, a recently developed popular semi numerical-analytical technique; differential transform method is employed to solve the reduced governing equations under the assumptions of velocity and thermal jump conditions on the disk surface. The combined effects of the velocity slip and temperature jump on the thermal and flow fields are investigated in great detail for different values of the nondimensional field parameters. In order to evaluate the efficiency of such rotating fluidic system, the entropy generation equation is derived and nondimensionalized. Additionally, special attention has been given to entropy generation, its characteristic and dependency on various parameters, i.e., group parameter, Kn and Re numbers, etc. It is observed that thermal and velocity jump strongly reduce the magnitude of entropy generation throughout the flow domain. As a result, the efficiency of the related physical system increases. A noticeable objective of this study is to give an open form solution of nonlinear field equations. The reduced recurative form of the governing equations presented gives the reader an opportunity to see the solution in open series form.

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