Showing papers on "Protoporphyrins published in 1970"

[20] S-adenosylmethionine: Magnesium protoporphyrin methyltransferase (Rhodopseudomonas spheroides and Euglena gracilis)

Abstract: Publisher Summary This chapter describes the assay, purification, and properties of magnesium protoporphyrin methyltransferase. This enzyme is involved in the biosynthesis of chlorophyll in plants and bacteriochlorophyll in photosynthetic bacteria. In Rhodopseudomonasspheroides, the enzyme is firmly attached to the chromatophores and to the cytoplasmic membrane. In Euglena gracilis, the enzyme appears to be in dual location; mostly, it is firmly attached to proplastids in dark-grown organisms or to chloroplast lamellae of cells grown in the light, but there is also some in the cytoplasm. The enzyme catalyzes the transfer of the labeled methyl group from S-adenosyl-(Me-14C)-methionine to magnesium protoporphyrin. The total porphyrin fraction is then purified, and the specific activity (expressed as counts per minute per millimicromole of total porphyrin) is determined. Knowing the specific activity of the S-adenosyl-(Me-14C)-methionine, the proportion of porphyrin present as monomethyl ester can be determined. Zinc, calcium, and magnesium protoporphyrins act as substrates for the enzyme. Magnesium complexes of deuteroporphyrin and mesoporphyrin are also active substrates.