Doriya Kruthi, Kumar Devarai Santhosh
Department of Chemical Engineering, Industrial Bioprocess and Bioprospecting Laboratory, Indian Institute of Technology Hyderabad, Room No: 530, Kandi Campus, Kandi, Medak Dist, Hyderabad, Telangana State, 502285, India.
3 Biotech. 2016 Dec;6(2):239. doi: 10.1007/s13205-016-0544-1. Epub 2016 Nov 12.
L-Asparaginase is a chemotherapeutic drug used in the treatment of acute lymphoblastic leukaemia (ALL), a malignant disorder in children. L-Asparaginase helps in removing acrylamide found in fried and baked foods that is carcinogenic in nature. L-Asparaginase is present in plants, animals and microbes. Various microorganisms such as bacteria, yeast and fungi are generally used for the production of L-asparaginase as it is difficult to obtain the same from plants and animals. L-Asparaginase from bacteria causes anaphylaxis and other abnormal sensitive reactions due to low specificity to asparagine. Toxicity and repression caused by bacterial L-asparaginase shifted focus to eukaryotic microorganisms such as fungi to improve the efficacy of L-asparaginase. Clinically available L-asparaginase has glutaminase and urease that may lead to side effects during treatment of ALL. Current work tested 45 fungal strains isolated from soil and agricultural residues. Isolated fungi were tested using conventional plate assay method with two indicator dyes, phenol red and bromothymol blue (BTB), and results were compared. L-Asparaginase activity was measured by cultivating in modified Czapek-Dox medium. Four strains have shown positive result for L-asparaginase production with no urease or glutaminase activity, among these C has high enzyme index of 1.57 and L-asparaginase activity of 33.59 U/mL. L-Asparaginase production by C was higher with glucose as carbon source and asparagine as nitrogen source. This is the first report focussing on fungi that can synthesize L-asparaginase of the desired specificity. Since the clinical toxicity of L-asparaginase is attributed to glutaminase and urease activity, available evidence indicates variants negative for glutaminase and urease would provide higher therapeutic index than variants positive for glutaminase and urease.
L-天冬酰胺酶是一种用于治疗急性淋巴细胞白血病（ALL，一种儿童恶性疾病）的化疗药物。L-天冬酰胺酶有助于去除油炸和烘焙食品中发现的具有致癌性的丙烯酰胺。L-天冬酰胺酶存在于植物、动物和微生物中。由于从植物和动物中难以获得L-天冬酰胺酶，各种微生物如细菌、酵母和真菌通常被用于生产L-天冬酰胺酶。来自细菌的L-天冬酰胺酶对天冬酰胺的特异性较低，会引起过敏反应和其他异常敏感反应。细菌L-天冬酰胺酶引起的毒性和抑制作用使人们将注意力转向真核微生物如真菌，以提高L-天冬酰胺酶的功效。临床上可用的L-天冬酰胺酶含有谷氨酰胺酶和脲酶，在治疗ALL期间可能会导致副作用。目前的研究测试了从土壤和农业残留物中分离出的45种真菌菌株。使用传统平板测定法，用两种指示染料苯酚红和溴百里酚蓝（BTB）对分离出的真菌进行测试，并比较结果。通过在改良的察氏培养基中培养来测量L-天冬酰胺酶活性。有四种菌株显示出产生L-天冬酰胺酶的阳性结果，且没有脲酶或谷氨酰胺酶活性，其中菌株C的酶指数高达1.57，L-天冬酰胺酶活性为33.59 U/mL。以葡萄糖作为碳源和天冬酰胺作为氮源时，菌株C产生的L-天冬酰胺酶更多。这是第一份聚焦于能够合成具有所需特异性的L-天冬酰胺酶的真菌的报告。由于L-天冬酰胺酶的临床毒性归因于谷氨酰胺酶和脲酶活性，现有证据表明，谷氨酰胺酶和脲酶呈阴性的变体比谷氨酰胺酶和脲酶呈阳性的变体具有更高的治疗指数。
