SUBSTRATE-ENZYME ORIENTATION DURING EMBRYONIC DEVELOPMENT

Abstract

The respiratory rates of whole embryos and cell-free breis were determined at various stages of development. During early stages, when the respiration of whole embryos is low, brei respiratory rate is high, the situation being reversed beyond about stage 17. Cytochrome oxidase remains uniformly high throughout development as shown by the effects of adding substrate to breis. Externally applied cytochrome oxidase substrates have little effect on intact embryos although the agents are shown to penetrate. Cytochrome C is shown not to be a limiting factor in brei respiration. Cyanide depresses the respiration of both breis and embryos. Azide has little effect on respiration of breis but is very effective in depressing oxygen consumption and development of intact embryos. The results are discussed in terms of spatial orientation of enzymes and substrates.