A rat gene encoding heart 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase

Abstract

There are at least 3 isozymes of 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase, a bifunctional enzyme which catalyzes the synthesis and degradation of fructose 2,6‐bisphosphate. A 22‐kb rat gene that encodes the heart isozyme has been identified and compared with the 55‐kb rat gene encoding the liver and muscle isozymes which had been described earlier. Although these 2 genes include 12 successive similar exons, they contain dissimilar exons at both ends, consistent with the occurrence of different regulatory domains at the N‐ and C‐termini in the 3 isozymes.

Cloning and expression of novel isoforms of 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase from bovine heart

“…1 show how the novel mRNAs identified here (B2 to B5) differ from the one (Bl) characterized earlier [12]. A comparison of their cDNA sequence with that of gene B [9] showed that they all derive from gene B. hence the nomenclature proposed.…”

“…Finally, the 3' noncoding sequence of clone 42 was interrupted between exons 13 and 14 ( Fig. 1) by 252 nucleotides that correspond to intron 111 of gene B [9].…”

“…Analysis of purified bovine heart PFK-2/ FBPase-2 by SDS/PAGE revealed two isozymes with M, values of 58,000 and 54,000 [8]. These isozymes derive from the same gene, called gene B [9], by alternative splicing [lO,l 11, the smaller isozyme lacking a peptide that contains sites for phosphorylation by PKA and PKC. This peptide corresponds to exon 15 of the rat gene, which contains 16 exons [9].…”

“…These isozymes derive from the same gene, called gene B [9], by alternative splicing [lO,l 11, the smaller isozyme lacking a peptide that contains sites for phosphorylation by PKA and PKC. This peptide corresponds to exon 15 of the rat gene, which contains 16 exons [9]. A cDNA fully coding for bovine heart PFK-2/FBPase-2 and containing exon 15 has been described [12].…”

Evidence for new phosphorylation sites for protein kinase C and cyclic AMP‐dependent protein kinase in bovine heart 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase

“…Two forms of PFK-2/FBPase-2 have heen identified in bovine heart with subunit M,s of 58,000 and 54,000 [6,7,11], wllich result from alternative splicing of the same primary transcript [7]. The 54,000 M, form of bovine heart PFK-UFBPase-2 differs from the 58,OW M, form in that it lacks a C-terminal peptide (residues 451-510), which is encoded by exon 15 in the rat gene [12] and which contains the phosphorylation sites for PKA and PKC; however, since the SS,ooO JJr form is also phosphorylated by both PKA and PKC [7], phosphorylation sites other than Ser-466 (WA) and Thr-475 (PKC) should be present in this form. In this paper we present evidence for new phosphorylation sites for PKA and PKC in bovine heart PFK-2/FBPase-2.…”