The antibiotic polyoxin D was shown to inhibit the incorporation of 14C-glucosamine into cell wall chitin in Neurospora crassa at levels which were comparable with those required for inhibition of fungal growth. At the same time, the antibiotic increased the accumulation of a nucleotide, which was identified as uridine diphosphate (UDP)-N-acetylglucosamine, indicating inhibition of chitin synthesis. Chitin synthetase (UDP-N-acetylglucosamine: chitin N-acetylglucosaminyl transferase, EC 2.4.1.16) of N. crassa was found to be strongly inhibited by polyoxin D, as determined by the transfer of 14C-N-acetylglucosamine from 14C-UDP-N-acetylglucosamine to the particulate fraction. The inhibition was competitive with respect to UDP-N-acetylglucosamine and specific for chitin synthetase. The Ki for polyoxin D in the reaction was 1.40 × 10?6m, and the Km for UDP-N-acetylglucosamine was 1.43 × 10?3m. The formation of osmotically sensitive, protoplast-like structures, when the fungus Cochliobolus miyabeanus was grown in the presence of polyoxin D, also suggested that the primary site of action of polyoxin D was in the formation of cell wall structures.
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机译：结果表明，抗生素多氧还蛋白D抑制 Neurospora crassa 中 14 C-葡萄糖胺掺入细胞壁几丁质的水平与抑制真菌生长所需的水平相当。同时，抗生素增加了核苷酸的积累，该核苷酸被鉴定为尿苷二磷酸（UDP）- N -乙酰氨基葡萄糖，表明甲壳质的合成受到抑制。 N的几丁质合成酶（UDP- N -乙酰氨基葡萄糖：几丁质 N -乙酰氨基葡萄糖氨基转移酶，EC 2.4.1.16）。从 14 中转移 14 C- N -乙酰氨基葡萄糖的方法测定，发现crassa 被多恶英D强烈抑制C-UDP- N -乙酰氨基葡萄糖的颗粒部分。该抑制物相对于UDP- N -乙酰基葡糖胺具有竞争性，并且对几丁质合成酶具有特异性。反应中多恶英D的 K i 为1.40×10 ？6 m， K N -乙酰氨基葡萄糖的> m 为1.43×10 ？3 m。当真菌 Cochliobolus miyabeanus 在多氧合蛋白D存在下生长时，渗透敏感的原生质体样结构的形成也表明，多氧合蛋白D的主要作用部位是细胞壁的形成。结构。
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