de Almeida F M, Lúcio A K, Polizeli M L, Jorge J A, Terenzi H F
Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Brazil.
FEMS Microbiol Lett. 1997 Oct 1;155(1):73-7. doi: 10.1111/j.1574-6968.1997.tb12688.x.
Two different trehalose-hydrolysing activities, known as acid or non-regulatory trehalases, and neutral or regulatory trehalases, have been recognised in a number of fungal species. The true role of these apparently redundant hydrolases remained obscure for many years. However, recent evidence suggests that neutral trehalases would be specialised in the mobilisation of cytosolic trehalose, while acid trehalases would only hydrolyse extracellular trehalose. Results obtained with Mucor rouxii, a Zygomycete initially thought to possess only neutral trehalase activity, reinforced this hypothesis. M. rouxii grows efficiently in trehalose as the sole carbon source. Trehalose-grown or carbon-starved cells exhibit a high trehalase activity of optimum pH 4.5, bound to the external surface of the cell wall, in contrast with the neutral (pH 6.5) trehalase, which occurs in the cytosol. Other differences between the neutral and the acid trehalases are the temperature optimum (35 degrees C and 45 degrees C, respectively) and thermal stability (half-life of 2.5 min and 12 min at 45 degrees C, respectively). The neutral trehalase, but not the acid trehalase, is activated in vitro by cAMP-dependent phosphorylation, stimulated by Ca2+, and inhibited by EDTA. It shows maximal activity at germination and decreases as growth proceeds. In contrast the activity of the acid trehalase is totally repressed in glucose-grown cultures and increases upon exhaustion of the carbon source, and is strongly induced by extracellular trehalose.
在许多真菌物种中已识别出两种不同的海藻糖水解活性，即酸性或非调节性海藻糖酶，以及中性或调节性海藻糖酶。多年来，这些明显多余的水解酶的真正作用一直不清楚。然而，最近的证据表明，中性海藻糖酶专门负责胞质海藻糖的动员，而酸性海藻糖酶仅水解细胞外海藻糖。用鲁氏毛霉（一种最初被认为仅具有中性海藻糖酶活性的接合菌）获得的结果强化了这一假设。鲁氏毛霉能以海藻糖作为唯一碳源高效生长。与存在于胞质溶胶中的中性（pH 6.5）海藻糖酶不同，在海藻糖上生长或碳饥饿的细胞表现出最佳pH为4.5的高海藻糖酶活性，该活性与细胞壁外表面结合。中性和酸性海藻糖酶之间的其他差异在于最适温度（分别为35℃和45℃）和热稳定性（在45℃下半衰期分别为2.5分钟和12分钟）。中性海藻糖酶而非酸性海藻糖酶在体外被cAMP依赖性磷酸化激活，受Ca2+刺激，并被EDTA抑制。它在萌发时表现出最大活性，并随着生长的进行而降低。相反，酸性海藻糖酶的活性在葡萄糖生长的培养物中被完全抑制，在碳源耗尽时增加，并受到细胞外海藻糖的强烈诱导。
