Relationship between age of culture and occurrence of the pigments of photosystem II of photosynthesis in heterocysts of a blue-green alga

Microspectrophotometric examination of the pigments in vivo of heterocysts of Anabaena sp. L-31 has shown that most heterocysts of 2-day-old cultures possess only very small amounts, if any, of c-phycocyanin, allo-phycocyanin, and c-phycoerythrin, the main pigments comprising photosystem II of photosynthesis. The quantities of these pigments, however, increase with age of cultures, and by the end of 5 days the majority of heterocysts contain comparatively large amounts. The culmination of this sequential development is observed in most heterocysts of 7- to 15-day-old cultures when the full complement of photosystem II pigments is present. The spectral characteristics at this stage are similar to those of vegetative cells and suggest a dedifferentiation of heterocysts.

Heme binding and transport--a spectrophotometric study of plasma glycoglobulin hemochromogens

A hitherto unreported phenomenon is the immediate production of the spectrum of ferrohemochromogens (in the presence of sodium dithionite) upon the addition in vitro of hydroxyhemin (pH 7.6-7.8) to the plasmas or sera, as well as to certain Cohn plasma protein fractions, of all mammalian species thus far examined. This distinctive reaction is characteristic of a coordination complex with heme iron, and is ascribed to a remarkable affinity for heme of certain plasma glycoglobulins, which include hemopexin. Spectrophotometry has permitted estimations of the specific heme-binding capacity (as ferrohemochromogen) of the plasmas, the rate of removal from plasma of injected heme, and the production of bile pigments therefrom. The study leads to a new proposal of the cooperative roles of the glycoglobulin hemochromogens and hematin-albumin in heme transport and bile pigment production.

Isotopic studies of the conversion of oxophlorins and their ferrihaems into bile pigments in the rat

1. Tritiated oxymesoporphyrins and their ferrihaems were tested as possible intermediates in the catabolism of haemoglobin. The tritiated compounds were injected into rats with biliary fistulae and the incorporation of the isotope into bile, bile pigment, urine, faeces, liver, kidney and spleen was measured. 2. alpha-Oxymesoferrihaem was extensively converted into bile pigment and specifically to the expected mesobilirubin. 3. beta-Oxymesoferrihaem was poorly converted into bile pigment and was not converted into mesobiliverdin IXbeta. The latter was independently shown to be excreted rapidly in bile. 4. The free oxyporphyrins were also poor precursors of bile pigment, and alpha-oxymesoporphyrin competed with bilirubin for excretion by the liver. 5. By analogy with the results obtained with alpha-oxymesoferrihaem it is concluded that alpha-oxyprotoferrihaem is an intermediate in the catabolism of haemoglobin, undergoing further oxidation to bile pigment under the catalysis of an enzyme of definite specificity.

Bile pigment formation in plants

The unicellular alga Cyanidium caldarium evolves carbon monoxide during the syntheis of the bile pigment, phycocyanobilin. Carbon monoxide and phycocyanobilin were produced in stoichiometric amounts at comparable rates. Therefore, the mechanism of bile pigment formation in this plant parallels that in mammals.

Carbon monoxide production associated with ineffective erythropoiesis

The rate of endogenous carbon monoxide production ( Vco), determined by the closed rebreathing system technique, was elevated above the normal range in four of five patients studied with ineffective erythropoiesis (four patients with primary refractory anemia, one with thalassemia). The mean molar ratio of Vco to Vheme (rate of circulating heme catabolism, determined from (51)Cr red cell survival curves) was 3.0 +/- 0.6 (SE), indicating that most of the CO originated from sources other than circulating erythrocyte hemoglobin, in contrast to previous findings in patients with hemolytic anemia, where Vco paralleled Vheme closely.After administration of glycine-2-(14)C to these patients, endogenous CO was isolated by washout of body CO stores at high pO(2) or by reacting peripheral venous blood samples with ferricyanide. The CO was then oxidized to CO(2) by palladium chloride and trapped for counting in a liquid scintillation spectrometer. "Early labeled" peaks of (14)CO were demonstrated which paralleled "early labeled" peaks of stercobilin and preceded maximal labeling of circulating heme. Production of "early labeled" (14)CO in patients with ineffective erythropoiesis was greatly increased, up to 14 times that found in a normal subject. The increased Vco and "early (14)CO" production shown by these patients are presumably related mainly to heme catabolism in the marrow. The possibility exists that hepatic heme and porphyrin compounds may also contribute significantly to Vco, as suggested by the finding of a high Vco in an additional patient with porphyria cutanea tarda.

Studies on haem alpha-methenyl oxygenase. Isomeric structure of formylbiliverdin, a possible precursor of biliverdin

1. The enzyme from guinea-pig liver that degrades pyridine-haemochromogen into formylbiliverdin, a possible precursor of biliverdin, breaks the porphyrin ring exclusively at the alpha-methene bridge. The enzyme is therefore appropriately named haem alpha-methenyl oxygenase. 2. It is deduced that this enzyme plays an essential role in haemoglobin catabolism in vivo.