Tissue distribution of placenta-type 6-phosphofructo- 2-kinase/fructose-2,6-bisphosphatase.

Several isozymes of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase have been characterized from mammalian tissues and, based on tissue origin, they are classified as liver, skeletal muscle, heart, testis, and placenta isozymes. In this paper, we examined the tissue distribution of placenta-type isozyme in rat tissues at the levels of transcription and translation. Analysis by Northern blotting showed that placenta, brain, testis, liver, kidney, and skeletal muscle expressed mRNA of placenta-type isozyme. Western blot analysis of fractions from POROS-HQ column chromatography of extracts from various rat tissues showed that proteins of placenta-type isozyme are expressed in placenta, brain, testis, liver, spleen, heart and lung, but not in kidney and skeletal muscle. An immunohistochemical study showed that, in liver, placenta-type isozyme is localized in Kupffer cells. These results indicate that isozymes of this particular enzyme may occur in particular cell types within each tissue.