Lamprey Fructose-1,6-bisphosphate Aldolase: Characterization of the Muscle-Type and Non-Muscle-Type Isozymes1

Zhang, Rong; Kusakabe, Takahiro; Iwanaga, Nariaki; Sugimoto, Yasushi; Kondo, Kosuke; Takasaki, Yozo; Imai, Toshio; Yoshida, Mitsutaka; Hori, Katsuji

doi:10.1006/abbi.1997.9918

Cited by 7 publications

(1 citation statement)

References 19 publications

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“…Interestingly, the K m values for F1P of turtle aldolase were not different between normoxic and anoxic states (both ∼14 mM) and were similar to the published value for humans (16 mM) [26]. In previous studies, the K m for FBP of liver aldolase has been determined to range between 900 nM in rabbits and squirrels [27], [28] and 1600 nM in humans and fish [29], [30]. In this study, the K m of turtle liver aldolase for FBP was found be approximately one order of magnitude lower than previously established values.…”

Section: Discussionsupporting

confidence: 81%

Characterization of Fructose-1,6-Bisphosphate Aldolase during Anoxia in the Tolerant Turtle, Trachemys scripta elegans: An Assessment of Enzyme Activity, Expression and Structure

2013

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One of the most adaptive facultative anaerobes among vertebrates is the freshwater turtle, Trachemys scripta elegans. Upon a decrease in oxygen supply and oxidative phosphorylation, these turtles are able to reduce their metabolic rate and recruit anaerobic glycolysis to meet newly established ATP demands. Within the glycolytic pathway, aldolase enzymes cleave fructose-1,6-bisphosphate to triose phosphates facilitating an increase in anaerobic production of ATP. Importantly, this enzyme exists primarily as tissue-specific homotetramers of aldolase A, B or C located in skeletal muscle, liver and brain tissue, respectively. The present study characterizes aldolase activity and structure in the liver tissue of a turtle whose survival greatly depends on increased glycolytic output during anoxia. Immunoblot and mass spectrometry analysis verified the presence of both aldolase A and B in turtle liver tissue, and results from co-immunoprecipitation experiments suggested that in the turtle aldolase proteins may exist as an uncommon heterotetramer. Expression levels of aldolase A protein increased significantly in liver tissue to 1.59±0.11-fold after 20 h anoxia, when compared to normoxic control values (P<0.05). A similar increase was seen for aldolase B expression. The overall kinetic properties of aldolase, when using fructose-1,6-bisphosphate as substrate, were similar to that of a previously studied aldolase A and aldolase B heterotetramer, with a Km of 240 and 180 nM (for normoxic and anoxic turtle liver, respectively). Ligand docking of fructose-1,6-bisphosphate to the active site of aldolase A and B demonstrated minor differences in both protein:ligand interactions compared to rabbit models. It is likely that the turtle is unique in its ability to regulate a heterotetramer of aldolase A and B, with a higher overall enzymatic activity, to achieve greater rates of glycolytic output and support anoxia survival.

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