Solubilization and selected properties of crambe seed thioglucosidase (thioglucoside glucohydrolase, EC 3.2.3.1)

Isolation of the epithiospecifier protein from oil-rape (Brassica napus ssp. oleifera) seed and its characterization

The epithiospecifier protein (ESP) is a myrosinase (MYR) cofactor, which is necessary to drive the MYR-catalyzed hydrolysis of some specific glucosinolates towards the production of cyanoepithioalkanes instead of isothiocyanates and nitriles. ESP was isolated from Brassica napus seeds by anionic exchange and gel filtration chromatography. ESP showed a molecular weight of about 39 kDa and pI 5.3. The amino acid sequence of several tryptic peptides of ESP (accounting for about 50% of the total sequence) made it possible to establish the high similarity (81% identity) with a hypothetical 37 kDa protein (TrEMBL data base accession number Q39104) and several jasmonate-inducible proteins from Arabidopsis thaliana. This observation suggests that ESP is likely to be involved in jasmonate-mediated defence and disease resistance mechanisms.

Indication of thioglucosidase activity in extracts of Neisseria gonorrhoeae

The recent demonstration of a host-derived inducer of gonococcal resistance to complement-mediated killing by human serum in purified serum and red blood cell fractions, which contained small glucopeptides with cysteine as one of the constituent amino acids, prompted an investigation of Neisseria gonorrhoeae for thioglucosidase activity. This involved an examination of supernatants of sonicated gonococci for thioglucoside hydrolysis by following, spectroscopically, the hydrolysis of 6-purine beta-D-glucothiopyranoside to 6-mercaptopurine and glucose. Extracts of N. gonorrhoeae were found to hydrolyse this thioglucoside. A substantial activity was present in a fraction with the same order of molecular weight as plant thioglucosidases. This led us to suspect the presence of a thioglucosidase in N. gonorrhoeae.

Rapeseed meal glucosinolates: metabolism and effect on performance in laying hens

Two experiments were conducted with Hyline Leghorn hens to study the metabolism and detrimental effects of rapeseed meal (RSM) glucosinolates. Raw Target RSM was force fed to 12 hens which were killed after varying time intervals (15 min., 30 min., 60 min.) and the contents of areas of the digestive tract (crop; proventriculus and gizzard; duodenum and ileum) were analyzed for the presence of hydrolysis products of progoitrin. Nitrile compounds were found to be present in all areas of the digestive tract in much larger relative amounts than was oxazolidinethione. When commercially prepared RSMs of varying glucosinolate content were fed to laying hens at a 50% level of dietary inclusion, high glucosinolate-content RSM depressed egg production (P less than 0.05) more than low glucosinolate-content RSM but did not cause a greater frequency of liver hemorrhage. Histological examination of liver tissues from hens suffering liver hemorrhage revealed a severe reticulolysis.