Improvement of Drosophila acetylcholinesterase stability by elimination of a free cysteine.

Background: Acetylcholinesterase is irreversibly inhibited by organophosphate and carbamate insecticides allowing its use for residue detection with biosensors. Drosophila acetylcholinesterase is the most sensitive enzyme known and has been improved by in vitro mutagenesis. However, it is not sufficiently stable for extensive utilization.

Kinetic comparison of tissue non-specific and placental human alkaline phosphatases expressed in baculovirus infected cells: application to screening for Down's syndrome.

Background: In humans, there are four alkaline phosphatases, and each form exhibits a characteristic pattern of tissue distribution. The availability of an easy method to reveal their activity has resulted in large amount of data reporting correlations between variations in activity and illnesses. For example, alkaline phosphatase from neutrophils of mothers pregnant with a trisomy 21 fetus (Down's syndrome) displays significant differences both in its biochemical and immunological properties, and in its affinity for some specific inhibitors.

Fetal sex and variations in kinetic properties of neutrophil alkaline phosphatase during the second trimester of normal pregnancy.

A kinetic parameter (the Vm/Km ratio), an index of neutrophil alkaline phosphatase catalytic efficiency, was studied in 36 women with normal pregnancies at 16-20 weeks' gestation. On each blood sample, determinations were achieved on enzyme extracted from maternal granulocytes by monitoring the phosphohydrolytic activity at 400 nm on a spectrophotometer equipped with software for computation of kinetic parameters. Infant sex was recorded at the delivery for all women included in this study.

Evaluation of two markers of cell maturation and proliferation in cultured amniotic cells of trisomic 18 fetuses at the 15th week of gestation.

Intensive studies have been conducted so far on biochemical markers available for screening of chromosome defects in obstetrical monitoring. In this paper we report further data on two protein phosphatases: alkaline phosphatase (a marker of cell maturation) and phosphotyrosine phosphatase (a marker of cell proliferation) assayed in cultured amniotic cells from fetuses with trisomy 18 at 15 weeks of gestation. Comparison with normal fetal cells showed a different behaviour for each enzyme: alkaline phosphatase was very significantly lowered while phosphotyrosine phosphatase remained a normal levels.

Inhibition by sodium thiophosphate and L-p-bromotetramisole of neutrophil alkaline phosphatase in normal and trisomy 21 pregnancies.

Alkaline phosphatase concentrations are known to increase in blood neutrophils of normal pregnant women. The main kinetic parameters of this enzyme were analysed and compared in a group of 30 women with normal pregnancies and a group of 11 women whose fetuses had trisomy 21 (Down's syndrome = DS). The subjects were studied at an identical stage of gestation.