with sodium borotritide. Whereas 1a was an efficient photoaffinity reagent for the beta-D-galactosidase from E. coli, 2a was ineffective. Three 3H-labelled peptides were isolated after digestion of the labelled enzyme with trypsin, one of which was an octapeptide (Trp 158 to Ser 165), which is remote from the segments detected as part of the active site of the enzyme.
3,7-
脱水-2-azi-1,2-二
脱氧-D-
甘油-L-
甘露糖-(8-3H)
辛醇++ +(1a)和3-
叠氮基1-
硫代-β-D-(6-3H通过与半
乳糖氧化酶反应,然后用
硼氢化钠还原,由未标记的化合物合成)
吡喃半
乳糖苷(2a)。1a是一种有效的大肠杆菌亲和性β-
D-半乳糖苷酶的光亲和试剂,而2a则无效。用胰
蛋白酶消化标记的酶后,分离出3个3H标记的肽,其中之一是八肽(Trp 158至Ser 165),该肽远离被检测为酶活性位点的片段。