Three Serum Enzymes in Twins

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Abstract
In a previous study (Hosenfeld and Schröter, 1970) we were able to demonstrate the activity of three serum enzymes, Cholinesterase (EC 3.1.1.8), ceruloplasmin (EC 1.10.3.2.) and alkaline phosphatase (EC 3.1.3.1) as individual characteristics which in healthy adults remain fairly constant for several months. For the purpose of investigating whether these quantitative features are genetically determined, we carried out similar studies on twins. The twins were traced in the Birth Register of Kiel. A certain amount of selection could have been caused by the willingness to have blood samples taken and by the interest in obtaining Accident Cards. We examined 30 MZ and 30 same-sexed DZ twin pairs, aged 8-20 years. The average age of the two groups of twins was about 15 years. Among the MZ 15 pairs were female; among the DZ, 11 pairs. Zygosity was established by polysymptomatic comparison of similarity. For documentation, color slides were made. ABO and Rh blood groups of all twins were determined, and in most cases further erythrocytic and serum properties. Blood samples were usually obtained in the afternoon about three to four hours after the last meal. The serum was centrifuged off and frozen. Enzyme determination was carried out during the next one to three weeks. Following substrates were used for estimation of the three enzymes: benzoylcholine, paraphenylendiamine and paranitrophenylphosphate. Acording to the methods of Richterich (1968), all measurements were carried out kinetically, employing a recording spectrophotometer (Beckman DB).