Chromones from Harrisonia perforata

Five new chromones, perforatins C-G, together with 10 known compounds were isolated from the wood of Harrisonia perforata.     

Change of thiamin-binding protein and thiamin levels during seed maturation and germination in sesame

Thiamin-binding proteins (TBPs) occur in many types of plant seeds. The biochemical and structural properties such as subunit structure and affinity for thiamin of the proteins have been characterized. However, the change of TBP and thiamin during seed maturation and germination is little known. Sesame (Sesamum indicum L.) seeds have unique albumin TBPs, because the other TBPs from plant seeds are generally globulins. In this study, we studied the change of the TBP and thiamin levels in sesame seeds. The protein content and thiamin-binding activity of the seeds increased with seed development after flowering. Immunological analysis using an antibody against the TBP of sesame seeds showed that the protein was accumulated in seeds during maturation. The thiamin content of the seeds increased with seed development after flowering. On the other hand, the thiamin-binding activity decreased during seed germination when TBP was degraded. The thiamin content of the seeds decreased during the germination. However, the amount of thiamin phosphate in the seeds during germination was little changed. These results suggested that thiamin was accumulated and stored as a complex with TBP in sesame seeds.     

Isolation and properties of gamma-tocopherol methyltransferase in Euglena gracilis.

Gamma-Tocopherol methyltransferase (EC2.1.1.-), which catalyzes the conversion of gamma-tocopherol into alpha-tocopherol, was present in a cell homogenate of Euglena gracilis. The enzyme was loosely bonded to the outer membrane of chloroplasts and solubilized from chloroplast membranes by a detergent, followed by partial purification in a three-step procedure. The methyltransferase showed a pH optimum of 7.5 and a temperature optimum of 35 degrees C and had an M(r) of 150,000. The activity was about 1.4-fold higher with gamma-tocopherol than with beta-tocopherol as substrate. The enzyme was specific for S-adenosylmethionine as a methyl donor, with a Km value of 50 microM. The addition of homogentisate, L-tyrosine and L-phenylalanine into a suspension of Euglena cells increased the relative pool sizes of alpha- and gamma-tocopherol, but not those of beta- and delta-tocopherol. The contents of alpha- and gamma-tocopherol in a chloroplast fraction of Euglena were always higher than those of any other fraction after any period of incubation with homogentisate. Based on the results of the present experiments, we propose a biosynthetic pathway of alpha-tocopherol in Euglena gracilis.