Rate limiting processes in the bohr shift in human red cells

Forster, R. E.; Steen, Johan B.

doi:10.1113/jphysiol.1968.sp008522

Cited by 37 publications

(22 citation statements)

References 12 publications

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“…If there had been a large contribution by carbamate formation this would have been apparent during carbonic anhydrase inhibition, since the enzyme plays no role in this process. However neither we nor Forster & Steen (1968) saw a rapid appearance of 02 followed by a slower second phase of 02 release when the enzyme was inhibited.…”

Section: T H Maren and E R Swenson Discussionmentioning

confidence: 99%

“…The half-time in duck and human is approximately 120 msec, while in the goosefish, dogfish and frog it ranges from 220 to 340 msec. Forster & Steen (1968) showed that the human Bohr effect at 37 'C has a half-time of 120 msec and at 23 0C of msec, values only slightly different from those of the cold-blooded species at 16 'C.…”

Section: T H Maren and E R Swenson Discussionmentioning

confidence: 99%

“…However in blood, the generation of the Bohr effect must also include the diffusion of CO2 and 02 through the red cell membrane and cytoplasm and the intracellular hydration-dehydration reactions of C02. The kinetics in intact human red cells have been studied by Craw, Constantine, Morello & Forster (1963) and Forster & Steen (1968). They showed the process has a half-time of 120 msec, a rate sufficient to yield equilibrium in 0-75-1 sec, the average capillary transit time.…”

Section: Introductionmentioning

confidence: 99%

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A comparative study of the kinetics of the Bohr effect in vertebrates.

Maren¹,

Swenson²

1980

The Journal of Physiology

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SUMMARY1. The kinetics of the Bohr effect and the role of carbonic anhydrase were studied in a series of representative vertebrates using a continuous flow rapid reaction apparatus.2. The rates of the Bohr effect in vertebrates are very similar, and differences among classes are manifestations of the ambient temperature.3. Complete carbonic anhydrase inhibition causes a fifteen to fortyfold reduction in the rate of the Bohr effect, sufficient to abolish its occurrence within capillary transit.4. There is a twenty-three-fold (duck) to 360-fold (man) excess of carbonic anhydrase activity in vertebrate red cells for the normal generation of the Bohr effect.5. When carbonic anhydrase is inhibited and CO2 hydration becomes rate limiting, the stoichiometry of the Bohr effect (Alog po2/ApH) is revealed in the ratio of the rates of proton formation in red cells to 02 release from haemoglobin.

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Section: T H Maren and E R Swenson Discussionmentioning

confidence: 99%

Section: T H Maren and E R Swenson Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A comparative study of the kinetics of the Bohr effect in vertebrates.

Maren¹,

Swenson²

1980

The Journal of Physiology

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“…More specifically, rbc CA catalyzes the hydration of CO 2 to HCO 3 -at the tissue site of production, and the dehydration of HCO 3 -to CO 2 at the respiratory surface, thereby facilitating the transport and excretion of CO 2 from the body (Perry, 1986;Perry and Laurent, 1990;Henry and Heming, 1998;Tufts and Perry, 1998;Geers and Gros, 2000;Henry and Swenson, 2000). In addition, rbc CA also facilitates the linkage of O 2 and CO 2 transport via the Bohr effect (Forster and Steen, 1968;Maren and Swenson, 1980). In mammals, there are two cytoplasmic CA isozymes in the rbc, CA I and II.…”

Section: Introductionmentioning

confidence: 99%

Tribute to R. G. Boutilier: Evidence of a high activity carbonic anhydrase isozyme in the red blood cells of an ancient vertebrate, the sea lamprey Petromyzon marinus

Esbaugh

Tufts

2006

Journal of Experimental Biology

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Carbonic anhydrase (CA) is a multi-functional enzyme that catalyzes the hydration/dehydration of carbon dioxide. In the red blood cell (rbc), CA is necessary to facilitate the transport of carbon dioxide out of the body. Results from earlier biochemical studies indicate that ancient vertebrates, such as agnathans, possess a low activity rbc CA isozyme, whereas more recently evolved vertebrates, such as teleost fish, possess a high activity isozyme. At present, however, the changes in the molecular structure that have resulted in this large increase in catalytic efficiency are unknown. The objective of the current study was therefore to determine the molecular structure of rbc CA in lampreys and compare it to that of teleosts in an effort to ascertain how this important enzyme became more efficient over evolutionary time. Isolation and sequencing of cytoplasmic CA from rbc and gill showed only a single isozyme of 789·bp (262 amino acids). This isozyme was also found in brain and kidney, with no evidence of additional cytoplasmic CA isozymes in other tissues. Phylogenetic analysis grouped this isozyme closely to vertebrate CA VII, which is ancestral to the rbc isozymes in other vertebrates. Interestingly, active site analysis revealed a structure similar to high activity isozymes. A comparative kinetic analysis of CA from rbc lysates and CA fusion proteins showed that the traditional method of determining the turnover number may not be appropriate for all vertebrate CAs. In contrast to previous evidence, lamprey CA was found to be a high activity isozyme. These results suggest that the critical functional characteristics of rbc CA have been highly conserved throughout vertebrate evolution.

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“…Further, the production of carbaminohaemoglobin could be neglected, because (a) equilibrium of CO2 and bicarbonate between the inside and outside of cells could be attained rapidly (Forster & Steen, 1968) and (b) the amount of CO2 produced during the deoxygenation ( = the amount of oxygen consumed by yeast, 200 /LM) corresponded to about 0 3 mmHg in CO2 tension. Thus, the effect of CO2 produced by bakers' yeast could be neglected.…”

Section: Properties Of Bakers' Yeast As An Oxygen Consuming Reagentmentioning

confidence: 99%

A method for studying oxygen diffusion barrier in erythrocytes: effects of haemoglobin content and membrane cholesterol.

Kon¹,

Maeda²,

Sekiya³

et al. 1980

The Journal of Physiology

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SUMMARY1. In order to study the kinetics of the oxygen egress from human red cells in the 50 sec-20 min time range, an apparatus for measuring the oxygen dissociation process was constructed, combining a spectrophotometer with an oxygen electrode of quick response. 3. The r value was always 1x0 for the haemolysate, but it was less than 1-0 for the normal red cells. Further, the oxygen dissociation curve of red cells obtained at higher Vmax was distorted, due to the non-equilibration between intra-and extracellular oxygen concentrations.4. The r value was (i) independent of the amounts of the allosteric effectors (2,3-diphosphoglycerate and H+) but (ii) dependent on the haemoglobin contents and (iii) dependent on the amounts of the membrane cholesterol. Therefore, the r value reflected only the process of the oxygen diffusion but not the 'chemical reaction' rate. The 'barrier' of the oxygen diffusion decreased at lower haemoglobin contents, but increased at higher cholesterol contents in the membrane.

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Rate limiting processes in the bohr shift in human red cells

Cited by 37 publications

References 12 publications

A comparative study of the kinetics of the Bohr effect in vertebrates.

A comparative study of the kinetics of the Bohr effect in vertebrates.

Tribute to R. G. Boutilier: Evidence of a high activity carbonic anhydrase isozyme in the red blood cells of an ancient vertebrate, the sea lamprey Petromyzon marinus

A method for studying oxygen diffusion barrier in erythrocytes: effects of haemoglobin content and membrane cholesterol.

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