Substrate specificity of chalcone synthase from Petroselinum hortense. Formation of phloroglucinol derivatives from aliphatic substrates.

The substrate specificity of chalcone synthase, the key enzyme of flavonoid biosynthesis, was investigated. A purified enzyme preparation from cell suspension cultures of parsley (Petroselinum hortense) catalyzed chain elongations with acetate units from malonyl-CoA, using various aromatic and aliphatic CoA esters as starter molecules. Malonyl-CoA could not be replaced by malonyl acyl carrier protein in the standard chalcone synthase assay. Butyryl-CoA, hexanoyl-CoA, and benzoyl-CoA served as substrates for the condensation reaction with similar efficiency as 4-coumaroyl-CoA, the natural substrate of the enzyme. Acetyl-CoA and octanoyl-CoA were relatively poor substrates. Among the products formed with the two most efficient aliphatic substrates tested, butyryl-CoA and hexanoyl-CoA, were the respective chalcone analogues, phlorobutyrophenone and phlorocaprophenone. The possibility is discussed that chalcone synthase and the corresponding enzyme of fatty acid synthesis in higher plants, beta-ketoacyl-acyl carrier protein synthase, have a common evolutionary origin.

[Above-average synthesis of anti-HAV by a booster effect after viral hepatitis A (author's transl)]. / Uberdurchschnittliche Anti-HAV-Synthese durch Booster-Effekte nach überstandener Virushepatitis A.

Above-average high antibody titres without repeat illness were obtained in 31 persons who, after having recovered from viral hepatitis A had renewed contact with the hepatitis-A virus. The titre was five to thirty-fold above the level usually observed after the initial infection. The time of second or third infection appears to be decisive for the level of the titre rise, which is probably a booster effect.

[Incidence of viral hepatitis in travelers in the tropics. Experiences with gamma globulin prophylaxis (author's transl)]. / Häufigkeit der Virushepatitis bei Tropenreisenden. Erfahrungen mit der Gammaglobulin-Prophylaxe

The occurrence of virus hepatitis during their residence was determined in 2755 persons returning from the tropics in 1975. The incidence was particularly high in those returning from India, Pakistan and Afghanistan. There was also a greater risk of the disease for travelers in Ethiopia, the countries on the West coast of Africa and some South American States. On the average, persons returning form the tropics fell ill 10 times more frequently with virus hepatitis during their residence in the tropics than in the Federal Republic. Particularly endangered occupational groups were the staffs of the health services and the social workers. Immunization with gamma globulins prevented an attack of virus hepatitis in all cases for a period of 4-6 months. Later, the effect of the immunization could no longer be established.

[Gammaglobulin prophylaxis of infectious hepatitis (author's transl)]. / Zur Frage der Gammaglobulin-Prophylaxe der infektiösen Hepatitis

When travelling in tropical areas and developing countries with deficient hygienic conditions, a distinctly greater risk of disease is observed with regard to infectious hepatitis. A prophylactic injection of gammaglobulin (5 ml i.m. for adults) for protection against diseases was found to be effective and expedient. A satisfactory protection can be assumed for a period of up to 4 months; after that, the prophylactic injection of gammaglobulin must be repeated in the same dosage, if there is a further risk of infection. It is strongly recommended that the prophylaxis be carried out at least for the first year of exposure to the risk, while later a gradual immunity possibly develops. Children should receive a reduced dose according to age.