摘要
外加5 mmol/L Ca^(2+)可以使菠菜PSⅡ颗粒的放氧活性增高。PSⅡ颗粒经EGTA透析、低pH值、光照、2 mol/L NaCl等处理后,放氧活性下降,同时,这些颗粒的钙含量也相应降低。但当外加 5 mmol/L Ca^(2+)时,可使这些颗粒全部或部分地恢复放氧活性。PSⅡ颗粒中存在的钙对放氧起着重要作用;钙在PSⅡ颗粒中的结合位点不止一个,其结合状态有紧密和松散之别。
The addition of 5 mmol/L Ca^(2+) to reactionmixture caused an increase of O_2-evolutionactivity in purified spinach PS Ⅱ particle pre-paration. The O_2-evolution activity decreasedafter different treatments of PS Ⅱ particles:(1) dialysis against EGTA, (2) treatment witha solution of low pH, (3) illumination, (4) wash-ing with 2 mol/L NaC1 (Table 1). The con-tent of Ca^(2+) in different particles were reducedsimultaneously (Table 4). Howevcr, the O_2-evolution activity could be completely or par-tly restored by the addition of 5 mmol/L Ca^(2+).The results show that: the Ca^(2+) in PS Ⅱ parti-cles is essential to O_2-evolution activity; thereare more than one binding site of Ca^(2+) in PS Ⅱparticles,with different degree of tightness.
