J. Biol. Chem., Vol. 262, Issue 21, 10114-10119, Jul, 1987
Phosphorylation in vivo of yeast (Saccharomyces cerevisiae) fructose- 1,6-bisphosphatase at the cyclic AMP-dependent site
J Rittenhouse, L Moberly and F Marcus
In vivo labeled fructose-1,6-bisphosphatase was immunopurified from yeast
(Saccharomyces cerevisiae) cells that had been incubated in the presence of
[32P] orthophosphate. Tryptic peptides from labeled enzyme were mapped by
high performance liquid chromatography. Most of the radioactivity was found
to be associated with the peptide Arg9 through Arg24, the same peptide
which had been previously shown to be phosphorylated in vitro by
cAMP-dependent protein kinase (Rittenhouse, J., Harrsch, P. B., Kim, J. N.,
and Marcus, F. (1986) J. Biol. Chem. 261, 3939-3943). The amino acid
sequence analysis suggests that phosphorylation occurs at the same site,
Ser11. We have also determined the extent of phosphorylation at Ser11 of
fructose-1,6-bisphosphatase in yeast cultures growing under various
nutritional conditions by measuring the relative amounts of phospho- and
corresponding dephosphopeptides in tryptic digests. Significant levels of
phosphorylation of the enzyme were found in yeast cultures grown under
gluconeogenic conditions that varied from 0.15 to 0.50 mol of phosphate per
mol of enzyme subunit. However, phosphate incorporation rapidly increased
to greater than 0.8 mol after addition of glucose to these cultures. An
alternative technique, based solely on enzyme activity measurements, was
also developed to estimate the extent of fructose-1,6- bisphosphatase
phosphorylation in yeast cultures. The results obtained with this technique
agreed with those obtained by high performance liquid chromatography of
tryptic peptides.