Actomyosin ATPase activities in the brachiopod Terebratalia transversa

1979 ◽  
Vol 57 (10) ◽  
pp. 1944-1949 ◽  
Author(s):  
William P. Eshleman ◽  
Jerrel L. Wilkens
Keyword(s):  
Inorganic Phosphate ◽  
Slow Rate ◽  
Metabolic Cost ◽  
Isotonic Contraction ◽  
Contractile System ◽  
Physiological Properties ◽  
Cross Bridges ◽  
Kinetics Of ◽  
Low Activity ◽  
Macromolecular Organization

Actomyosin specific adenosine triphosphate (AM-ATPase) activities of muscles of the articulate brachiopod Terebratalia transversa were determined in an attempt to understand some of their unusual physiological properties. The striated adductors, smooth adductors, and ventral adjustors have activities of 0.318, 0.089, and 0.050 μmol of inorganic phosphate per minute per milligram of protein respectively, which correlate with their contraction rates and behaviors. The suggestion that sudden compliance to stretch in the diductor muscles (slip) is due to simultaneous breakage of all cross bridges is supported by the low activity of 0.022 μmol of inorganic phosphate per minute per milligram of protein. This rate of activity is not as low as expected from the extremely slow rate of isometric contraction (186 min) but it does correlate with the faster rate of isotonic contraction observed after removal of the antagonistic smooth adductors. Slippage represents a previously unknown extreme in the macromolecular organization and kinetics of a contractile system, an elegant adaptation of articulate brachiopods to minimize the metabolic cost of keeping the valves open while allowing rapid closure in an emergency.

scholarly journals A Novel Pseudomonas geniculata AGE Family Epimerase/Isomerase and Its Application in d-Mannose Synthesis

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1809
Author(s):  
Zhanzhi Liu ◽  
Ying Li ◽  
Jing Wu ◽  
Sheng Chen
Keyword(s):  
3D Structure ◽  
Three Dimensional ◽  
Optimal Temperature ◽  
Reaction Conditions ◽  
Enzymatic Production ◽  
Physiological Properties ◽  
Potential Applications ◽  
Kinetics Of ◽  
Optimal Reaction ◽  
Gene Age

d-mannose has exhibited excellent physiological properties in the food, pharmaceutical, and feed industries. Therefore, emerging attention has been applied to enzymatic production of d-mannose due to its advantage over chemical synthesis. The gene age of N-acetyl-d-glucosamine 2-epimerase family epimerase/isomerase (AGEase) derived from Pseudomonas geniculata was amplified, and the recombinant P. geniculata AGEase was characterized. The optimal temperature and pH of P. geniculata AGEase were 60 °C and 7.5, respectively. The Km, kcat, and kcat/Km of P. geniculata AGEase for d-mannose were 49.2 ± 8.5 mM, 476.3 ± 4.0 s−1, and 9.7 ± 0.5 s−1·mM−1, respectively. The recombinant P. geniculata AGEase was classified into the YihS enzyme subfamily in the AGE enzyme family by analyzing its substrate specificity and active center of the three-dimensional (3D) structure. Further studies on the kinetics of different substrates showed that the P. geniculata AGEase belongs to the d-mannose isomerase of the YihS enzyme. The P. geniculata AGEase catalyzed the synthesis of d-mannose with d-fructose as a substrate, and the conversion rate was as high as 39.3% with the d-mannose yield of 78.6 g·L−1 under optimal reaction conditions of 200 g·L−1d-fructose and 2.5 U·mL−1P. geniculata AGEase. This novel P. geniculata AGEase has potential applications in the industrial production of d-mannose.

The Kinetics of Inorganic Phosphate Uptake and Utilization by Chick Heart Mitochondria

1988 ◽  
pp. 313-323
Author(s):  
Peter P. Toth ◽  
Britton Chance ◽  
John E. Sell ◽  
John F. Holland ◽  
Shelagh Ferguson-Miller ◽  
...  
Keyword(s):  
Inorganic Phosphate ◽  
Phosphate Uptake ◽  
Heart Mitochondria ◽  
Chick Heart ◽  
Kinetics Of

Direct Method for Determining Inorganic Phosphate in Serum with the "CentrifiChem"

1972 ◽  
Vol 18 (3) ◽  
pp. 263-265 ◽  
Author(s):  
John A Daly ◽  
Gerhard Ertingshausen
Keyword(s):  
Inorganic Phosphate ◽  
Direct Method ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Kinetics Of ◽  
A Direct Method

Abstract A direct method was developed for determining inorganic phosphate in serum, which requires only a single reagent addition. The method quantitates the unreduced phosphomolybdate heteropolyacid at 340 nm and is linear to at least 10 mg of phosphate per 100 ml. Only 10 µl of serum is required. The unique blanking capabilities of centrifugal analyzers permit the "on run" elimination of serum and reagent background absorbances, which are automatically subtracted. Data on precision, correlation, and recovery are presented. Kinetics of the reaction were studied, and theoretical limits of automatic blanking when applied to a first-order reaction are discussed.

Effects of BAPTA on force and Ca2+ transient during isometric contraction of frog muscle fibers

1998 ◽  
Vol 275 (2) ◽  
pp. C375-C381 ◽  
Author(s):  
Y.-B. Sun ◽  
C. Caputo ◽  
K. A. P. Edman
Keyword(s):  
Mechanical Performance ◽  
Muscle Fibers ◽  
Frog Muscle ◽  
Clear Correlation ◽  
Bathing Solution ◽  
Control Value ◽  
Contractile System ◽  
Intracellular Ca ◽  
Cross Bridges ◽  
Reduced State

The effects of 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid (BAPTA) on force and intracellular Ca2+ transient were studied during isometric twitches and tetanuses in single frog muscle fibers. BAPTA was added to the bathing solution in its permeant AM form (50 and 100 μM). There was no clear correlation between the changes in force and the changes in Ca2+ transient. Thus during twitch stimulation BAPTA did not suppress the Ca2+ transient until the force had been reduced to <50% of its control value. At the same time, the peak myoplasmic free Ca2+concentration reached during tetanic stimulation was markedly increased, whereas the force was slightly reduced by BAPTA. The effects of BAPTA were not duplicated by using another Ca2+ chelator, EGTA, indicating that BAPTA may act differently as a Ca2+ chelator. Stiffness measurements suggest that the decrease in mechanical performance in the presence of BAPTA is attributable to a reduced number of active cross bridges. The results could mean that BAPTA, under the conditions used, inhibits the binding of Ca2+ to troponin C resulting in a reduced state of activation of the contractile system.

Effect of palmitoyl-CoA and β-oxidation of fatty acids on the kinetics of mitochondrial citrate transporter

1976 ◽  
Vol 54 (2) ◽  
pp. 171-177 ◽  
Author(s):  
Surinder Cheema-Dhadli ◽  
Mitchell L. Halperin
Keyword(s):  
Fatty Acids ◽  
Inorganic Phosphate ◽  
Mitochondrial Protein ◽  
Maximum Velocity ◽  
Citrate Transporter ◽  
Kinetics Of

The kinetics of the hepatic mitochondrial citrate transporter were studied using 1,2,3-benzene tricarboxylate and the inhibitor-stop technique at 8 °C. The apparent Km for this transporter was 250 μM and the maximum velocity was 2 nmol of citrate transported per minute per milligram of mitochondrial protein. This apparent Km was increased when hepatic mitochondria were preincubated with both L-palmitoylcarnitine and CoA-SH but not with either alone. This rise in apparent Km was accompanied by a rise in the acid insoluble CoA-SH content. Removal of mitochondrial acid insoluble CoA by 'defatted albumin' resulted in a parallel decrease in the apparent Km. The apparent Km for the citrate transporter was increased after coupled β-oxidation of L-palmitoylcarnitine or octanoate without a detectable increase in acid insoluble CoA. Inhibition of β-oxidation of L-palmitoylcarnitine by the D-derivative prevented the rise in the apparent Km. Preincubation with ATP resulted in an increase in this apparent Km. When L-palmitoylcarnitine oxidation occurred without ATP accumulation (hexokinase, glucose, ADP, and inorganic phosphate) the apparent Km for the citrate transporter increased two- to threefold.Therefore, the apparent Km for the citrate transporter varied directly with the acid insoluble CoA content. In addition, this Km was increased as a result of β-oxidation of fatty acids but the mechanism was not solely attributable to a rise in acid insoluble CoA or ATP. The physiological implications of these findings are discussed.

Kinetics of Intramuscular Inorganic Phosphate During Low Intensity Exercise With Blood Flow Restriction

2009 ◽  
Vol 41 ◽  
pp. 140-141
Author(s):  
Masato Sugaya ◽  
Satoshi Fujita ◽  
Riki Ogasawara ◽  
Hayao Ozaki ◽  
Mikako Sakamaki ◽  
...  
Keyword(s):  
Blood Flow ◽  
Inorganic Phosphate ◽  
Blood Flow Restriction ◽  
Flow Restriction ◽  
Low Intensity ◽  
Low Intensity Exercise ◽  
Kinetics Of
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