A novel amino acid, di-isodityrosine, has been isolated from hydrolysates of cell walls of tomato cell culture. Analysis by UV spectrometry, partial derivatization with 2,4-dinitrofluorobenzene and mass and NMR spectrometry show that the compound is composed to two molecules of isodityrosine, joined by a biphenyl linkage. The possible reactions involved in the formation of this molecule in vivo are discussed, as is the possibility that it could form an interpolypeptide linkage between cell wall proteins such as extensin, and hence aid in the insolubilization of the protein in the wall.

Homogalacturonan is an ancient streptophyte feature, albeit secondarily lost in Klebsormidium. When conquering the land, the first embryophytes already possessed rhamnogalacturonan-I. In contrast, charophyte and land-plant hemicelluloses differ substantially, indicating major changes during terrestrialization. The presence of 3-MeGal in charophytes and lycophytes but not in the 'intervening' bryophytes confirms that cell-wall chemistry changed drastically between major phylogenetic grades.

No abstract

No abstract

The amino acid leucine is efficiently used by the trypanosomatid Leishmania mexicana for sterol biosynthesis. The incubation of [2- These results are compatible with two routes by which the leucine skeleton may enter intact into the isoprenoid pathway. The catabolism of leucine could generate HMG-CoA that is then directly reduced to MVA for incorporation into sterol. Alternatively, a compound produced as an intermediate in leucine breakdown to HMG-CoA (e.g. dimethylcrotonyl-CoA) could be directly reduced to produce an isoprene alcohol followed by phosphorylation to enter the isoprenoid pathway post-MVA.