Correlation between the Presence of Ubiquitin Conjugated Protein Phosphatase Inhibitor 1 and Postmortem Muscle Glycogen Metabolism

Abstract

Recently, we have identified the ubiquitin conjugate, protein phosphatase inhibitor 1 (I1), from postmortem muscles. Since I1 is one of the important regulators of glycogen metabolism, the effect of this conjugate (Ub-I1) present in postmortem muscle on glycolysis was investigated. Two sample groups were distinguishable: those not containing Ub-I1 (I, n=5) and those containing Ub-I1 (II, n=27). Due to the enormous variation in ultimate pH at 48 h postmortem, the latter group was subcategorized into a IIa group showing lower or normal pH and a IIb group showing higher or dark, firm, dry meat pH. Postmortem glycolysis occurred rapidly and vigorously among group I samples. The rate and extent of postmortem glycolysis was typical in group IIa samples while it was slower and weaker in group IIb samples although they had similar glycolytic potential. This discrepancy between sample groups IIa and IIb corresponded to the Ub-I1 abundance. Thus, the relative Ub-I1 abundance appears to correlate with postmortem glycolysis.