Enzyme-gold cytochemistry of seed xyloglucans using two xyloglucan-specific hydrolases. Importance of prior heat-deactivation of the enzymes.

摘要: Two pure, homogeneous xyloglucan-hydrolyzing enzymes from germinated nasturtium seeds have been used to localize xyloglucans specifically in seed cell walls. The enzymes, a novelendo (1→4)-β-d-glucanase which shows absolute specificity towards and β-d-galactosidase is capable of removing galactosyl residues polymeric xyloglucans, were stabilize gold sols. complexes applied ultrathin sections (Tropaeolum majus L) tamarind (Tamarindus indica seeds. prepared the active enzyme proteins retained activity, such gave extremely weak section-labelling or no labelling at all. When subjected heat-deactivation before being sols, obtained lacked but strong, specific sections. was checked by substrate-competition, pretreatment with heat-denaturated comparing xyloglucan-containing storage cells other types same section. maximal pH optimal for enzyme. We conclude that enzyme-gold retain high activity against substrate be localized are likely unsuitable as cytochemical probes because they may causein situ modification. In case described here localization heat deactivated attributable retention heat-treated enzymatically-inactive recognition. Alternatively, some recovery native configuration heat-denatured protein occurred on adsorption surface colloidal particle.