Purification and isoenzymic composition of glycogen phosphorylase b from normal and abnormal (PSE) muscles

Ion exchange chromatography and preparative isoelectric focusing allowed the identification of five isoenzymes of glycogen phosphorylase b from the longissimus dorsi muscle of normal pigs and those prone to having pale, soft and exudative (PSE) muscle. The isoelectric point of the isoenzymes varied in the pH range from 6.29 to 6.55. One of them, with an isoelectric point at about a pH of 6.49, accounts for 65% of the total glycogen phosphorylase b activity. No significant differences between normal and PSE-prone pigs were observed in the total glycogen phosphorylase b activity and in the isoenzyme distribution pattern. It is concluded that the fast glycogen turnover in PSE-prone pigs is not due to a different isoenzyme pattern of phosphorylase b.