Hormonal induction of alkaline phosphatase activity by an increase in catalytic efficiency of the enzyme

摘要: Abstract Alkaline phosphatase activity of HeLa 65 cells is increased 5- to 20-fold during growth in medium containing cortisol. The kinetics increase are characterized by a 12- 24-hour lag period after adding hormone, followed linear and rapid which reaches plateau 60 100 hours. Both RNA protein synthesis required for “induction”. However, immunological methods show that the amount enzyme induced not increased; suggesting there neither an rate alkaline nor hormone-mediated decrease catabolism enzyme. When induction compared using radioactively labeled specific precipitation antiserum, maximally long before maximum. This finding suggests hormone acts initiating modifier molecule interacts with produce enhanced catalytic efficiency. physical chemical characteristics base-level similar except V max much greater. efficiency result zinc ion content this metalloenzyme. binding ionic form apoenzyme appears be different from It suggested alteration produces entatic effect, lowering energy requirements substrate transition state.