Department of Horticulture, University of Wisconsin, 53706, Madison, Wisconsin, USA.
Planta. 1974 Dec;119(4):267-78. doi: 10.1007/BF00388330.
Mesophyll protoplasts and bundle-sheath cells of Pennisetum purpureum Schum., a C4 plant with low phenol-oxidase activity, were enzymatically separated according to methods recently developed with sugarcane (Saccharum officinarum L.), maize (Zea mays L.), and sorghum (Sorghum bicolor L.). The phosphoenolpyruvate carboxylase and NADP-malic dehydrogenase of the C4 pathway were found to be localized in the mesophyll protoplasts while ribulose-1,5-diphosphate (RuDP) carboxylase, phosphoribulokinase and NADP-malic enzyme were localized in the bundle-sheath cells. The levels of these enzyme activities in the leaf extracts and in certain cellular preparations of P. purpureum are sufficient to account for the rate of photosynthesis in the leaf. These results on the activities and distribution of photosynthetic enzymes with P. purpureum preparations are consistent with our previous evidence for cellular separation of the C4 and the reductive pentose-phosphate pathways in C4 species.With chlorogenic acid as the substrate, P. purpureum, Setaria lutescens (Weigel) Hubb. and Panicum texanum Buckl. have relatively low phenol-oxidase activity, similar to that found in spinach (Spinacia oleracea L.); while sorghum, sugarcane, maize, Panicum capillare L. and P. miliaceum L. have relatively high phenoloxidase activity, similar to that in tobacco (Nicotiana tabacum L.). C4 species having high phenol-oxidase activity have substantial activity of the enzyme in both mesophyll and bundle-sheath extracts. Since phenol oxidase is found in both cell types it is not logical to expect preferential inhibition of RuDP carboxylase or other photosynthetic enzymes through phenol oxidation in mesophyll extracts, as has been previously suggested. When dithiothreitol and polyvinylpyrrolidone were included in the enzyme extraction medium, the activity of RuDP carboxylase increased 10% in P. purpureum and 59% in sugarcane leaf extracts.
采用最近甘蔗（Saccharum officinarum L.）、玉米（Zea mays L.）和高粱（Sorghum bicolor L.）酶分离方法，从低酚氧化酶活性的 C4 植物，普通狗尾草（Pennisetum purpureum Schum.）中酶解分离出叶肉原生质体和维管束鞘细胞。发现 C4 途径的磷酸烯醇丙酮酸羧化酶和 NADP-苹果酸脱氢酶定位于叶肉原生质体中，而核酮糖-1,5-二磷酸（RuDP）羧化酶、磷酸核酮糖激酶和 NADP-苹果酸酶定位于维管束鞘细胞中。从普通狗尾草叶片提取物和某些细胞制剂中获得的这些酶活性水平足以解释叶片的光合作用速率。这些关于普通狗尾草酶活性和分布的结果与我们之前关于 C4 物种中 C4 和还原戊糖磷酸途径细胞分离的证据一致。
以绿原酸为底物，普通狗尾草、柳枝稷（Weigel）Hubb.和梯牧草（Panicum texanum Buckl.）的酚氧化酶活性相对较低，与菠菜（Spinacia oleracea L.）相似；而高粱、甘蔗、玉米、梯牧草和黍米（P. miliaceum L.）的酚氧化酶活性相对较高，与烟草（Nicotiana tabacum L.）相似。具有高酚氧化酶活性的 C4 物种在叶肉和维管束鞘提取物中均具有大量的酶活性。由于酚氧化酶存在于两种细胞类型中，因此不能期望通过叶肉提取物中的酚氧化作用对 RuDP 羧化酶或其他光合作用酶进行优先抑制，正如之前所提出的那样。当在酶提取介质中包含二硫苏糖醇和聚乙烯吡咯烷酮时，普通狗尾草和甘蔗叶片提取物中 RuDP 羧化酶的活性分别增加了 10%和 59%。
