Abstract
1.
1. 6-Phosphofructo-1-kinase (PFK) isoenzymes were studied in the jejunal mucosa of rabbit, rat and mouse.
2.
2. The rat mucosal enzyme was found to be very similar to, although not identical with, the mouse mucosal enzyme, as the physical and regulatory properties of these two enzymes were nearly similar except that the immunological studies were dissimilar.
3.
3. PFK prepared from rabbit mucosa showed different and distinct properties from the rat and mouse mucosal PFK when studied by (NH
4)
2SO
4-precipitation, polyacrylamide gel electrophoresis, immunological cross-reactivity and regulatory properties.
4.
4. The difference between the rabbit enzyme and the rat or mouse enzymes is suggested to be due to the lower rate of glycolysis observed in the rabbit jejunal mucosa as the total enzyme activities of the rabbit were found to be less than half of those activities of the rat and mouse mucosa.
5.
5. The dissimilarities among the species in mucosal isoenzymes obtained in the present study are rather expected since the term isoenzyme is now properly reserved for forms that have been shown to be genetically distinct as shown for different tissues in the same species. Such multigenic control does not appear to have been established for the same tissue in different species.