Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, Wisconsin 58706, USA.
Dev Biol. 1981 Jun;84(2):407-16. doi: 10.1016/0012-1606(81)90409-7.
The four earliest developmentally controlled enzymes in the cellular slime mold, Dictyostelium discoideum, accumulate during axenic growth in rich media. We have shown that at low cell titers the specific activities of N-acetylglucosaminidase, alpha-mannosidase, leucine aminopeptidase, and alanine transaminase are each at very low or vegetative levels comparable to amoebae which have been grown on bacteria as the food source. During the exponential phase of growth all four enzymes accumulate dramatically reaching cellular specific activities at least as high as during development. The magnitude of this accumulation is influenced by alterations in the growth medium. We suggest that these results, combined with those of prior investigations, indicate that a restricted segment of early development is initiated during axenic growth. This means that growth and early development are not mutually exclusive events in this organism. The secretion of lysosomal enzymes is also affected by the composition of the growth media. In all media, including growth in bacterial suspensions, lysosomal enzymes are secreted in significant quantities. There is a correspondence in the effects of media composition on the secretion of these enzymes and on the regulation of developmentally controlled enzymes during axenic growth. The secretion of lysosomal enzymes that are not developmentally regulated is affected in these media, suggesting that the regulation and secretion of these enzymes are under separate control. It is clear that studies of the regulation of lysosomal enzymes in this organism must take into account the secretion of the enzymes as well as their cellular specific activities to properly reflect levels of gene expression.
细胞黏菌（Dictyostelium discoideum）的四个最早发育控制酶在丰富培养基中的无菌生长过程中积累。我们已经表明，在低细胞浓度下，N-乙酰氨基葡萄糖苷酶、α-甘露糖苷酶、亮氨酸氨肽酶和丙氨酸转氨酶的比活性非常低或处于与以细菌为食源的变形虫相当的营养生长水平。在生长的指数期，所有四种酶都显著积累，达到的细胞比活性至少与发育过程中一样高。这种积累的幅度受生长介质的改变的影响。我们认为，这些结果与先前的研究结果相结合，表明在无菌生长过程中启动了早期发育的受限阶段。这意味着在这个生物体中，生长和早期发育不是相互排斥的事件。溶酶体酶的分泌也受生长培养基组成的影响。在所有培养基中，包括在细菌悬浮液中的生长，溶酶体酶都以大量分泌。在这些酶的分泌和无菌生长过程中发育控制酶的调节方面，培养基组成的影响存在对应关系。在这些培养基中，不受发育调节的溶酶体酶的分泌受到影响，这表明这些酶的调节和分泌受到单独的控制。显然，在该生物体中研究溶酶体酶的调节必须考虑到酶的分泌以及它们的细胞比活性，以正确反映基因表达的水平。
