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Characterization of the hemoglobins of the Australian lungfish Neoceratodus forsteri (Krefft)

Citation

Rasmussen, JR and Wells, RMG and Henty, K and Clark, TD and Brittain, T, Characterization of the hemoglobins of the Australian lungfish Neoceratodus forsteri (Krefft), Comparative Biochemistry and Physiology. Part B, 152, (2) pp. 162-167. ISSN 1096-4959 (2009) [Refereed Article]

DOI: doi:10.1016/j.cbpa.2008.09.015

Abstract

We examined for the first time the hemoglobin components of the blood of the Australian lungfish, Neoceratodus forsteri and their functional responses to pH and the allosteric modulators adenosine triphosphate (ATP), guanosine triphosphate (GTP), 2,3-bisphosphoglyceric acid (BPG) and inositol hexaphosphate (IHP) at 25 C. Lysates prepared from stripped, unfractionated hemolysate produced sigmoidal oxygen equilibrium curves with high oxygen affinity (oxygen partial pressure required for 50% hemoglobin saturation, p50 = 5.3 mmHg) and a Hill coefficient of 1.9 at pH 7.5. p50 was 8.3 and 4.5 mmHg at pH 6 and 8, respectively, which corresponded to a modest Bohr coefficient (Δlog p50/ΔpH) of − 0.13. GTP increased the pH sensitivity of oxygen binding more than ATP, such that the Bohr coefficient was − 0.77 in the presence of 2 mmol L− 1 GTP. GTP was the most potent regulator of hemoglobin affinity, with concentrations of 5 mmol L− 1 causing an increase in p50 from 5 to 19 mm Hg at pH 7.5, while the order of potency of the other phosphates was IHP > ATP > BPG. Three hemoglobin isoforms were present and each contained both α and β chains with distinct molecular weights. Oxygen affinity and pH-dependence of isoforms I and II were essentially identical, while isoform III had a lower affinity and increased pH-dependence. The functional properties of the hemoglobin system of Neoceratodus appeared consistent with an active aquatic breather adapted for periodic hypoxic episodes.

Item Details

Item Type:Refereed Article
Keywords:lungfish, hemoglobin, oxygen affinity, Bohr effect
Research Division:Biological Sciences
Research Group:Zoology
Research Field:Animal behaviour
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Coastal or estuarine biodiversity
UTAS Author:Clark, TD (Dr Timothy Clark)
ID Code:103423
Year Published:2009
Web of Science® Times Cited:5
Deposited By:IMAS Research and Education Centre
Deposited On:2015-10-08
Last Modified:2015-10-08
Downloads:0

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