Peptidase Activity in Human Serum following Bone Fracture.

In a previous communication (Barber et al. [1 ] ) it has been shown that there exists in human serum a cobalt-activatable enzyme which splits 1leucylglycylglycine (LGG). The rate of hydrolysis in normal adult individuals is between 5.5 and 8.5% per hour (in the previous communication the rate of hydrolysis of LGG by serum of normal adult controls was stated to be 6.1 to 7.8%o per hour. This value had to be revised on the basis of more subjects investigated since then). This investigation was originally planned for the clinical study of tissue reactions of the ageing organism. The present communication is not immediately related to this problem but seems to have considerable pathophysiological significance: following fractures there was found to be an abnormal rise in the activity of the LGG-splitting enzyme in human serum. Ever since the studies by Cuthbertson (2) and Browne (3) and their co-workers, numerous clinical and experimental investigations have been made on the metabolic aspects of injury and repair. There have been many attempts to explain these observations on the basis of one hypothesis but so far no single mechanism has been discovered which could account for the irregularities of protein metabolism accompanying injury and repair. Therefore, every new observation is significant in spite of the fact that its functional meaning may not be clear on the basis of our present-day concepts.