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The preparation of a dimethyltetrahtdrouroporphyrin (Faktor II or sirohydrochlorin) using suspensions of Propionibacterium shermanii as well as a promising method for the isolation of tetrapyrrols with at least four carboxy substituents from cell-free extracts and growth media are described. Also a Faktor II-analogue with three methyl groups which are derived from L-methionine is reported. Incorporation experiments indicate that this is an intermediate in cobyrinic acid formation. Because of this, and from spectroscopic (field desorptionmass, visible absorption) studies it is concluded that the "extra" methyl group is located at the meso-carbon between two methylated reduced rings.

Clostridium tetanomorphum and Propionibacterium shermanii were examined for intermediates in the synthetic pathway uroporphyrinogen III leads to cobyrinic acid. The isolation of two novel methylated hydroporphyrins, whose methyl groups are derived from S-adenosyl-L-methionine, is described. Spectroscopic (field desorption-mass, visible absorption) und electrophoretic studies as well as incorporation of labelled substrates indicate that they are analogues of a dihyrouroporphyrin and a tetrahydrouroporphyrin with adjacent reduced rings. Field desorption spectra of the [C2H3]- and [CH3]-tetrahydrouroporphyrin analogues show that the compound contains two methyl groups; it is concluded that the chlorine-like compound has one methyl group. Dehydrogenation experiments indicate that the methyl groups are located at one beta-carbon of the reduced rings. Incorporation experiments suggest that the tetrahydrouroporphyrin-like compound is an intermediate in cobyrinic acid biosynthesis. Studies on the utilization of a heptacarboxyporphyrinogen from C. tetanomorphum for cobyrinic acid formation are also described.