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Table 4 Adenylate activation of wood frog skeletal muscle AMPD from control versus frozen frogs

From: Regulation of 5'-adenosine monophosphate deaminase in the freeze tolerant wood frog, Rana sylvatica

  Control Frozen
  Free AMPD Bound AMPD Free AMPD Bound AMPD
K a Mg·ATP, mM 1.90 ± 0.03 NE 0.63 ± 0.04 a NE
Mg·ATP fold-activation 1.53 ± 0.09 NE 2.69 ± 0.20 a NE
K a Mg·ADP, mM 1.12 ± 0.15 b 3.75 ± 0.37 0.54 ± 0.02 ab 1.14 ± 0.10 a
Mg·ADP fold-activation 2.17 ± 0.29 1.25 ± 0.21 5.01 ± 0.69 a 3.42 ± 0.24 a
  1. Data are means ± SEM, for determinations on Sephadex G50-filtered muscle extracts from n = 4 individual frogs. Significantly different from a the corresponding value in control frogs, b the corresponding value for bound AMPD in control frogs, by the Student's t-test, P < 0.05. NE, no effect. K a is the activator concentration that produces half-maximal activation; values were determined at 0.5 mM AMP. K a and fold activation values were calculated using a nonlinear least-squares regression kinetics program [39].