Nucleus Hydrolytic enzymes

The spermatozoon consists of a head, a midpiece and a tail or flagellum. The head contains the nucleus and a vesicle known as the acrosome (Figure 19.4). It contains hydrolytic enzymes that are required during fertilisation of the ovum. 

Fig. 6 Illustration of the PCI principle. The photosensitizer and the macromolecular therapeutics (here visualized by a nanoparticle for gene delivery) are endocytosed as indicated and accumulating in endocytic vesicles. The nanoparticle may be degraded by hydrolytic enzymes in late endosomes or lysosomes, translocated to the cytosol by intrinsic properties of the designed nanoparticle or released into the cytosol by a photochemically induced rupture of the endocytic vesicle as illustrated by the use of a diodelaser. The DNA may thereafter enter the nucleus for transgene expression...

Biochemists have demonstrated at least 80 different enzymes in preparations of nuclei. Among them are enzymes of the main bioenergetic pathways and a large number of hydrolytic enzymes. On the basis of their relationship to the nucleus, the enzymes in nuclear preparations can be divided into three different groups (1) those likely to be contaminants (2) those clearly related to the nucleus and (3) those present in the nucleus. 

A discussion of all the enzymes known to be associated with the nucleus is unnecessary for the purposes of this text however, it might be valuable to review the nuclear association of some hydrolytic enzymes. The presence of adenosine triphosphatase in the nucleus remains controversial. Although some investigators found it in large amounts, none was present in the nuclear preparations of others but since dinitro-phenol, which activates mitochondrial adenosine triphosphatase, has no effect on the nuclear enzyme, it seems that nuclear adenosine triphosphatase is different from the mitochondrial enzyme. The association of phosphorylase with the nucleus is also puzzling it is not clear what part the enzyme plays in the synthesis or breakdown of nuclear glycogen. 

Figure 14.10 Overview of cellular entry of (non-viral) gene delivery systems, with subsequent plasmid relocation to the nucleus. The delivery systems (e.g. lipoplexes and polyplexes) initially enter the cell via endocytosis (the invagination of a small section of plasma membrane to form small membrane-bound vesicles termed endosomes). Endosomes subsequently fuse with golgi-derived vesicles, forming lysosomes. Golgi-derived hydrolytic lysosomal enzymes then degrade the lysosomal contents. A proportion of the plasmid DNA must escape lysosomal destruction via entry into the cytoplasm. Some plasmids subsequently enter the nucleus. Refer to text for further details...

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