Kacprzak Magdalena M, Lewandowska Irmina, Matthews Rowena G, Paszewski Andrzej
Department of Genetics, Institute of Biochemistry and Biophysics, PAS, Pawinskiego 5a, 02-106 Warsaw, Poland.
Biochem J. 2003 Dec 1;376(Pt 2):517-24. doi: 10.1042/BJ20030747.
Roles played by homocysteine and choline in the regulation of MS (methionine synthase) have been examined in fungi. The Aspergillus nidulans metH gene encoding MS was cloned and characterized. Its transcription was not regulated by methionine, but was enhanced by homocysteine and repressed by choline and betaine. MS activity levels were regulated in a similar way. The repression by betaine was due to its metabolic conversion to choline, which was found to be very efficient in A. nidulans. Betaine and choline supplementation stimulated growth of leaky metH mutants apparently by decreasing the demand for methyl groups and thus saving methionine and S -adenosylmethionine. We have also found that homocysteine stimulates transcription of MS-encoding genes in Saccharomyces cerevisiae and Schizosaccharomyces pombe.
在真菌中研究了同型半胱氨酸和胆碱在甲硫氨酸合酶(MS)调节中的作用。编码MS的构巢曲霉metH基因被克隆并进行了表征。其转录不受甲硫氨酸调节,但受同型半胱氨酸增强,并受胆碱和甜菜碱抑制。MS活性水平也以类似方式调节。甜菜碱的抑制作用是由于其代谢转化为胆碱,这在构巢曲霉中被发现非常有效。补充甜菜碱和胆碱显然通过降低对甲基的需求,从而节省甲硫氨酸和S-腺苷甲硫氨酸,刺激了渗漏型metH突变体的生长。我们还发现同型半胱氨酸刺激酿酒酵母和粟酒裂殖酵母中编码MS的基因的转录。