Premium
The different pH optima and substrate specificities of extracellular and vacuolar invertases from plants are determined by a single amino‐acid substitution
Author(s) -
Goetz Marc,
Roitsch Thomas
Publication year - 1999
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1999.00628.x
Subject(s) - invertase , biochemistry , proline , extracellular , valine , amino acid , residue (chemistry) , biology , enzyme , raffinose , saccharomyces cerevisiae , chemistry , yeast , sucrose
Summary Different plant invertase isoenzymes are characterized by a single amino‐acid difference in a conserved sequence, the WEC‐P/V‐D box. A proline residue is present in this sequence motif of extracellular invertase sequences, whereas a valine is found at the same position of vacuolar invertase sequences. The role of this distinct difference was studied by substituting the proline residue of extracellular invertase CIN1 from Chenopodium rubrum with a valine residue, by site‐directed muta‐ genesis. The mutated gene was heterologously expressed in an invertase‐deficient Saccharomyces cerevisiae strain. The single amino‐acid difference was shown to be the molecular basis for two enzymatic properties of invertase isoenzymes, for both the pH optimum and the substrate specificity. A proline in the WEC‐P/V‐D box determines the more acidic pH optimum and the higher cleavage rate of raffinose of extracellular invertases, compared to vacuolar invertases that have a valine residue at this position.