Enzymic and structural studies on processed proteins from the vacuolar (lutoid-body) fraction of latex of Hevea brasiliensis

T Subroto, H de Vries, JJ Schuringa, UMS Soedjanaatmadja, J Hofsteenge, PA Jekel, JJ Beintema*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

22 Citations (Scopus)

Abstract

The lutoid-body (bottom) fraction of latex from the rubber tree (Hevea brasiliensis) contains a limited number of major proteins. These are the chitin-binding protein hevein, its precursor and C-terminal fragment of the precursor, a basic chitinase/lysozyme, and a beta-1,3-glucanase. The content and properties of the latter enzyme differ between lutoid-body fractions from four different rubber clones (cultivars). While the enzyme from clone GT.1 is a glycoprotein with carbohydrate attached to two glycosylation sites, the enzymes from other clones contain little or no carbohydrate. Latex from clone GT.1 has a higher beta-1,3-glucanase content than those from the other three clones, but with a significantly lower specific activity. The enzyme exhibits a pH optimum at 4.5, but there is a second one at 6.7. Peptides isolated from beta-1,3-glucanase of clone GT.1 showed that the enzyme is heterogeneous at the C-terminus, probably as a result of removal of a vacuolar targeting sequence by an endopeptidase, followed by further removal of C-terminal residues by a carboxypeptidase-like activity. This incomplete digestion can be related to glycosylation at the extreme C-terminus of the mature enzyme. Non-glycosylated Hevea beta-1,3-glucanases exhibit less C-terminal heterogeneity. A homologue of the antifungal protein osmotin was isolated from rubber clones which are less susceptible to fungal diseases. Another identified protein is identical to a citrate binding protein (CBP), already sequenced as cDNA, but with cleaved-off N-terminal signal and C-terminal vacuolar targeting peptides. Four C-terminal propeptides of vacuolar proteins in Hevea are positively identified, which is a valuable contribution to previously known examples of this type of processing. (C) 2001 Editions scientifiques et medicales Elsevier SAS.

Original languageEnglish
Pages (from-to)1047-1055
Number of pages9
JournalPlant Physiology and Biochemistry
Volume39
Issue number12
Publication statusPublished - Dec-2001

Keywords

  • citrate-binding protein
  • glucanase
  • Hevea brasiliensis
  • osmotin
  • rubber latex
  • GLYCOSYL HYDROLASES
  • BETA-1,3-GLUCANASE
  • CHITINASE
  • LATICIFERS
  • CATALYSIS
  • THAUMATIN
  • SEQUENCE
  • FAMILIES
  • LYSOZYME
  • DEFENSE

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