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Erythroid carbonic anhydrases of developing chick embryos. Coordinate expression with primitive and definitive
Insights
Chick embryo red blood cells exhibit carbonic anhydrase activity with distinct developmental peaks. Two molecular forms of carbonic anhydrase type II are present, with one replacing the other during development.
Area of Science:
- Biochemistry
- Developmental Biology
- Enzymology
Background:
- Carbonic anhydrases are crucial enzymes involved in various physiological processes.
- Erythroid carbonic anhydrase plays a significant role in carbon dioxide transport in red blood cells.
Purpose of the Study:
- To determine the erythroid carbonic anhydrase activity during chick embryonic development.
- To characterize the molecular forms of carbonic anhydrase in developing chick erythrocytes.
Main Methods:
- Measurement of enzyme activity in chick embryo haemolysates.
- Purification of enzyme molecular forms using affinity chromatography.
- Isoelectrofocusing analysis to identify and differentiate enzyme forms.
Main Results:
- Erythroid carbonic anhydrase activity showed minor peaks at 3, 9, and 15 days, and a major peak at 19 days of incubation.
- Only carbonic anhydrase type II was detected in embryonic red cells, similar to adults.
- Two distinct molecular forms of carbonic anhydrase type II were identified: an early form and a late form.
- The late form, identical to the adult enzyme, appeared around 6-7 days and replaced the early form.
- Primitive and definitive erythroid cells showed compartmentalization of the early and late forms, respectively.
Conclusions:
- Chick embryonic erythroid carbonic anhydrase activity changes dynamically during development.
- The transition from the early to the late form of carbonic anhydrase type II reflects cellular differentiation.
- This study elucidates the developmental regulation and compartmentalization of carbonic anhydrase isozymes in avian erythropoiesis.
Abstract:
Erythroid carbonic anhydrase activity of chick embryos from the 3rd day of incubation to the egg hatching has been determined. Three minor activity peaks at 3, 9 and 15 days of development and a major one at 19 days were found. The enzyme molecular forms were purified by affinity chromatography from haemolysates of embryos at several stages of development. As has been found for the adult erythrocytes, only type II isozyme was detected in the embryo red cells. Isoelectrofocusing analysis demonstrated that two different molecular forms of this isozyme are synthesized by the red cells of developing embryos. Only the early form is present up to 5 days of development; the late form, which is indistinguishable from the adult isozyme, appears in the haemolysate at 6-7 days and quickly replaces the early form. Analysis of purified primitive and definitive erythroid lines from 7-days-old embryos showed a compartmentalization of the early and late forms into the primitive and definitive erythroid cells, respectively.