Bertolini M C, Laramée L, Thomas D Y, Cygler M, Schrag J D, Vernet T
Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec.
Eur J Biochem. 1994 Jan 15;219(1-2):119-25. doi: 10.1111/j.1432-1033.1994.tb19921.x.
The fungus Geotrichum candidum produces extracellular lipases. Purification and characterization of different lipase isoforms from various G. candidum strains is difficult due to the close physical and biochemical properties of the isoforms. Consequently, the characterization of these enzymes and their substrate specificities has been difficult. We have determined the lipase genes present in four strains of G. candidum (ATCC 34614, NRCC 205002, NRRL Y-552 and NRRL Y-553) by molecular cloning and DNA sequencing. Each strain contains two genes similar to the previously identified lipase I and lipase II cDNAs. Our data suggest that no other related lipase genes are present in these strains. Each lipase-gene family shows sequence variation (polymorphism) that is confirmed by Southern-blot analysis. This polymorphism and the sequence differences between lipase I and lipase II have been localized within the previously determined three-dimensional structure of lipase II. Although most of the amino acid substitutions are located on the protein surface, some are present in structural features possibly involved in determining substrate specificity.
白地霉可产生细胞外脂肪酶。由于不同白地霉菌株的脂肪酶同工型在物理和生化性质上较为相近，因此从各种白地霉菌株中纯化和鉴定不同的脂肪酶同工型具有一定难度。所以，对这些酶及其底物特异性的鉴定一直颇具困难。我们通过分子克隆和DNA测序，确定了四株白地霉（ATCC 34614、NRCC 205002、NRRL Y - 552和NRRL Y - 553）中存在的脂肪酶基因。每株菌株都含有两个与先前鉴定的脂肪酶I和脂肪酶II cDNA相似的基因。我们的数据表明，这些菌株中不存在其他相关的脂肪酶基因。每个脂肪酶基因家族都表现出序列变异（多态性），这一点通过Southern杂交分析得到了证实。这种多态性以及脂肪酶I和脂肪酶II之间的序列差异已定位在先前确定的脂肪酶II三维结构内。尽管大多数氨基酸替换位于蛋白质表面，但有些存在于可能参与确定底物特异性的结构特征中。
