Postmortem Regulation of Glycolysis by 6Phosphofructokinase in Bovine Muscle

1
Postmortem Regulation of Glycolysis by
6-Phosphofructokinase in Bovine Muscle
R.D. Rhoades and S. B. Smith Department of
Animal Science, Texas AM University,TX 77843
Hypothesis
Results

• Rate of inactivation of PFK determines ultimate
  pH, not initial glycogen concentration.

Objectives

• Determine the pH sensitivity of PFK.
• Determine glycolytic intermediate concentrations
  over time postmortem.

Methods

• Obtained postmortem muscle samples from 6
  randomly-selected steers.
• Excised longissimus muscle from the 13th thoracic
  rib location at intervals from 40 min to 24 h.
• Measured glycolytic intermediates and PFK
  activity by spectrophotometric methods.

Conclusions

• After 100 minutes, there was a steady increase in
  G6P and F6P concentrations.
• PFK activity was depressed by nearly 50 percent
  when pH was reduced to 7.0.
• Postmortem decline in pH ultimately inactivates
  PFK, which halts glycogen depletion.
• We conclude that the rate of inactivation of PFK,
  not initial glycogen concentrations, dictates
  ultimate pH in beef.