UDP-GLUCOSE PYROPHOSPHORYLASE FROM POTATO-TUBER - CDNA CLONING AND SEQUENCING

We have isolated a cDNA encoding UDP-glucose pyrophosphorylase from a cDNA library of immature potato tuber using oligonucleotide probes synthesized on the basis of partial amino acid sequences of the enzyme. The cDNA clone contained a 1,758-base-pair insert including the complete message for UDP-glucose pyrophosphorylase with 1,431 base pairs. The amino acid sequence of the enzyme inferred from the nucleotide sequence consists of 477 amino acid residues. All the partial amino acid sequences determined protein-chemically [Nakano et at. (1989) J. Biochem. 106, 528-532] confirmed the primary structure of the enzyme. An N-terminal-blocked peptide was isolated from the proteolytic digest of the enzyme protein, and the blocking group was deduced to be an acetyl group by fast atom bombardment-mass spectrometry. On the basis of the predicted amino acid sequence (477 residues minus the N-terminal Met plus an acetyl group), the molecular weight of the enzyme monomer is calculated to be 51,783, which agrees well with the value determined by polyacrylamide gel electrophoresis. In the eDNA structure, the open-reading frame is preceded by a 125-base-pair non region, which contains a sequence being homo logous with the consensus sequence for plant genes, and is followed by a 174-base-pair noncoding sequence including a polyadenylation signal. Amino acid sequence comparisons revealed that the potato U1)P-glucose pyrophosphorylase is homologous to the enzyme from slime mold, Dictyostelium discoideum, but not to ADP-glucose pyrophosphorylases from rice seed and E8cherichia coli. © 1990 Copyright, 1990 by the Journal of Biochemistry.