S. 1996. Proteolylic activity in the maize pollen wali, -Physiol. Plant, 98: i72-17S, A new protease from maize {Zea may.'; L,) pollen is described. It was purified using gel filtration, ion exchange and high performance liquid ehromatography, SDS-PAGE and HPLC showed that the enzyme ha,s a dimeric stracture of M, ca 60 000, Inhibitor investigations indicated an aspartic acid residue in it,s active site. The optimum pH for maize pollen aspartic proteinase activity was 5,6, and the optimum temperature was 45°C, The enzyme is easily eluted from the pollen grains and, as confimied by enzymoblotting after isoelectric focusing, it is located in the pollen wall. Similar to metallo-proteinases, its activity is inhibited by Zn'*, The pi value for purified aspartic proteinase, as estimated after IEF, was 5,0, Two-dimensional electrophoresis analysis of proteins eluted from maize pistils suggests that the enzyme digests the proteins and may be involved in pollen-tuix germination. The properties of serine and aspartic proteinases from maize pollen are compared.

Twelve enzymes from mature pollen grains of maize were separated by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The separation in the second dimension was both in the presence and absence of sodium dodecyl sulfate (SDS). Ten of the investigated enzymes lost activity after separation in the presence of SDS, but those of esterases and acid phosphatase could be recovered. On the other hand, 2-D electrophoresis without SDS is suitable for the analysis of maize pollen pectinesterase, malate dehydrogenase, glutamic-oxalacetic transaminase, diaphorase, superoxide dismutase, and phosphoglucose isomerase. 1-D PAGE and isoelectric focusing (IEF) are sufficient to analyze glucose-6-phosphate dehydrogenase, alcohol dehydrogenase, shikimic dehydrogenase, and glutamate dehydrogenase. The possibility of applying 2-D electrophoresis for the analysis of enzymes from single stigma and stigma exudate is dicussed.

A new protease from maize (Zea mays L.) pollen is described. It was purified using gel filtration, ion exchange and high performance liquid chromatography. SDS‐PAGE and HPLC showed that the enzyme has a dimeric structure of M, ca 60,000. Inhibitor investigations indicated an aspartic acid residue in its active site. The optimum pH for maize pollen aspartic proteinase activity was 5.6, and the optimum temperature was 45°C. The enzyme is easily eluted from the pollen grains and, as confirmed by enzymoblotting after isoelectric focusing, it is located in the pollen wall. Similar to metallo‐proteinases, its activity is inhibited by Zn2+. The pL value for purified aspartic proteinase, as estimated after IEF, was 5.0. Two‐dimensional electrophoresis analysis of proteins eluted from maize pistils suggests that the enzyme digests the proteins and may be involved in pollen‐tube germination. The properties of serine and aspartic proteinases from maize pollen are compared.