Wagemaker Matthijs J M, Eastwood Daniel C, van der Drift Chris, Jetten Mike S M, Burton Kerry, Van Griensven Leo J L D, Op den Camp Huub J M
Department of Microbiology, IWWR Radboud University Nijmegen, Toernooiveld 1, 6525 ED, Nijmegen, The Netherlands.
Appl Microbiol Biotechnol. 2006 Jul;71(4):486-92. doi: 10.1007/s00253-005-0185-5. Epub 2005 Nov 10.
Fruit body initials of Agaricus bisporus contain high levels of urea, which decrease in the following developmental stages until stage 4 (harvest) when urea levels increase again. At storage, the high urea content may affect the quality of the mushroom, i.e. by the formation of ammonia from urea through the action of urease (EC 3.5.1.5). Despite the abundance of urea in the edible mushroom A. bisporus, little is known about its physiological role. The urease gene of A. bisporus and its promoter region were identified and cloned. The coding part of the genomic DNA was interrupted by nine introns as confirmed by cDNA analysis. The first full homobasidiomycete urease protein sequence obtained comprised 838 amino acids (molecular mass 90,694 Da, pI 5.8). An alignment with fungal, plant and bacterial ureases revealed a high conservation. The expression of the urease gene, measured by Northern analyses, was studied both during normal development of fruit bodies and during post-harvest senescence. Expression in normal development was significantly up-regulated in developmental stages 5 and 6. During post-harvest senescence, the expression of urease was mainly observed in the stipe tissue; expression decreased on the first day and remained at a basal level through the remaining sampling period.
双孢蘑菇的子实体原基含有高水平的尿素，在随后的发育阶段尿素含量会降低，直到第4阶段（收获期）尿素含量再次增加。在储存过程中，高尿素含量可能会影响蘑菇的品质，例如通过脲酶（EC 3.5.1.5）的作用使尿素形成氨。尽管可食用蘑菇双孢蘑菇中尿素含量丰富，但其生理作用却鲜为人知。双孢蘑菇的脲酶基因及其启动子区域已被鉴定和克隆。cDNA分析证实，基因组DNA的编码部分被9个内含子打断。获得的首个完全同源担子菌脲酶蛋白序列包含838个氨基酸（分子量90,694 Da，pI 5.8）。与真菌、植物和细菌脲酶的比对显示出高度保守性。通过Northern分析测定脲酶基因的表达，在子实体正常发育过程和采后衰老过程中均进行了研究。在正常发育过程中，脲酶基因在第5和第6发育阶段表达显著上调。在采后衰老过程中，脲酶的表达主要在菌柄组织中观察到；在第一天表达下降，并在剩余的采样期内维持在基础水平。
