Tomato and Aspergillus niger pectinesterases. Correlation of differences in existing reports: large species variations.

Existing reports on the enzyme tomato pectinesterase differ in alignments of two internal segments and in many single-residue replacements. The alignment from cDNA data, with a 317-residue mature protein, is correct, but protein analyses also show at least 18 single-residue replacements, suggesting the presence of many native or (less likely) cloning-derived microheterogeneities. Purification of Aspergillus niger pectinesterase and N-terminal sequence analysis of this enzyme reveal a different structure and indicate an extensive protein divergence.