Synthesis of the cyanogenic β-glucosidase, linamarase, in white clover

Abstract

The β-glucosidase, linamarase, which specifically hydrolyzes cyanogenic substrates, linamarin and lotaustralin, in white clover, is synthesized in the early stages of leaf and seedling development in genetically competent plants. Plants, from natural populations, possessing at least one Li allele synthesize linamarase but plants with only li alleles do not, nor do they produce inactive but antigenically related linamarase. Linamarase is known to be a mannosyl glycoprotein, which in its active form is a dimer, with a subunit size of 62,000 M r. We demonstrate that the antibiotic tunicamycin, which prevents N-acetyl-asparagine linked glycosylation, reduces in vivo synthesis of linarmarase. In vitro translation of mRNA from a Li Li plant yields a 59,000 M r immunoprecipitated linamarase polypeptide which is modified to a 62,000 M r product by the addition of dog pancreas microsomes. No anti-linamarase immunoprecipitable product is obtained from the in vitro translation products of mRNA from a li li plant.