Department of Biochemistry and Biophysics, University of California, Davis, California 95616.
Plant Physiol. 1970 Nov;46(5):720-7. doi: 10.1104/pp.46.5.720.
Inorganic sulfate enters the mycelia of Aspergillus nidulans, Penicillium chrysogenum, and Penicillium notatum by a temperature-, energy-, pH-, ionic strength-, and concentration-dependent transport system ("permease"). Transport is unidirectional. In the presence of excess external sulfate, ATP sulfurylase-negative mutants will accumulate inorganic sulfate intracellularly to a level of about 0.04 m. The intracellular sulfate can be retained against a concentration gradient. Retention is not energy-dependent, nor is there any exchange between intracellular (accumulated) and extracellular sulfate. The sulfate permease is under metabolic control. Sulfur starvation of high methionine-grown mycelia results in about a 1000-fold increase in the specific sulfate transport activity at low external sulfate concentrations. l-Methionine is a metabolic repressor of the sulfate permease, while intracellular sulfate and possibly l-cysteine (or a derivative of l-cysteine) are feedback inhibitors. Sulfate transport follows hyperbolic saturation kinetics with a Michaelis constant (Km) value of 6 x 10(-5) to 10(-4)m and a V(max) (for maximally sulfurstarved mycelia) of about 5 micromoles per gram per minute. Refeeding sulfur-starved mycelia with sulfate or cysteine results in about a 10-fold decrease in the V(max) value with no marked change in the Km. Azide and dinitrophenol also reduce the V(max.).
无机硫酸盐通过一种温度、能量、pH 值、离子强度和浓度依赖的转运系统（“渗透酶”）进入 Aspergillus nidulans、Penicillium chrysogenum 和 Penicillium notatum 的菌丝体。转运是单向的。在过量的外部硫酸盐存在下，ATP 硫酸酯酶阴性突变体将无机硫酸盐在细胞内积累到约 0.04 m 的水平。细胞内硫酸盐可以保留在浓度梯度之外。保留不是能量依赖性的，细胞内（积累的）和细胞外硫酸盐之间也没有任何交换。硫酸盐渗透酶受代谢控制。高蛋氨酸生长的菌丝体的硫饥饿导致在低外部硫酸盐浓度下硫酸盐特异性转运活性增加约 1000 倍。l-蛋氨酸是硫酸盐渗透酶的代谢抑制剂，而细胞内硫酸盐和可能的 l-半胱氨酸（或 l-半胱氨酸的衍生物）是反馈抑制剂。硫酸盐转运遵循双曲线饱和动力学，米氏常数（Km）值为 6 x 10(-5) 到 10(-4)m，最大硫饥饿菌丝体的 V(max)值约为 5 微摩尔/克/分钟。用硫酸盐或半胱氨酸重新喂养硫饥饿的菌丝体导致 V(max)值降低约 10 倍，而 Km 值没有明显变化。叠氮化钠和二硝基苯酚也降低了 V(max)。
