S-alk(en)yl-L-cysteine sulfoxides, alliinase and aroma in Leucocoryne.

Levels of S-alk(en)yl-L-cysteine sulfoxides, alliinase and enzymatically generated pyruvic acid were determined in the bulb, leaf and scape of five species and a natural hybrid of Leucocoryne (Liliaceae), a genus of ornamental geophytes indigenous to Chile. (+)-S-Methyl-L-cysteine sulfoxide (MCSO) was present in all plant parts of all species at levels between 0.09 and 1.41 mg g(-1) fr. wt. Trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide (PRENCSO) was present in plant parts of three species only (L. angustipetala, L. oadorata and L. purpurea) at levels between 0.12 and 1.82 mg g(-1) fr. wt. No other S-alk(en)yl-L-cysteine sulfoxides were detected. Alliinase (EC 4.4.1.4) was detected in the leaf, bulb and scape of L. angustipetala and L. purpurea, only in the leaves of L. coquimbensis and L. purpurea x L. coquimbensis, and only in the bulb of L. odorata. Enzymatically generated pyruvic acid was detected in all plant parts of all species at levels between trace amounts and 5.33 micromol g(-1) fr. wt. As PRENCSO is produced only in Leucocoryne species exhibiting a strong and unpleasant onion-like aroma, it is probable that the enzymatic degradation of PRENCSO is the main cause of that aroma. Consequently, Leucocoryne cultivars should be selected in species and hybrids that lack the ability to synthesise PRENCSO.

A novel alliinase from onion roots. Biochemical characterization and cDNA cloning.

We have purified a novel alliinase (EC 4.4.1.4) from roots of onion (Allium cepa L.). Two isoforms with alliinase activity (I and II) were separated by concanavalin A-Sepharose and had molecular masses of 52.7 (I) and 50.5 (II) kD on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 51 (I) and 57.5 (II) kD by gel filtration fast-protein liquid chromatography. Isoform I had an isoelectric point of 9.3, while isoform II had isoelectric points of 7.6, 7.9, 8.1, and 8.3. The isoforms differed in their glycosylation. Both contained xylose/fucose containing complex-type N-linked glycans, and isoform II also contained terminal mannose structures. Both isoforms had activity with S-alk(en)yl-L-cysteine sulfoxides. Unlike other allium alliinases, A. cepa root isoforms had cystine lyase activity. We cloned a gene from A. cepa root cDNA and show that it codes for A. cepa root alliinase protein. Homology to other reported allium alliinase genes is 50%. The gene coded for a protein of mass 51.2 kD, with two regions of deduced amino acid sequence identical to a 25- and a 40-amino acid region, as determined experimentally. The A. cepa root alliinase cDNA was expressed mainly in A. cepa roots. The structure and function of the alliinase gene family is discussed.

Peer review of psychotherapeutic treatments in psychiatry: a review of the literature.

This paper reviews the literature concerning the current status of peer review of psychotherapeutic treatments in psychiatry. Accounts of the aims and mechanisms of peer review, administrative issues and the effects of peer review on patient care and professional practice are examined.