Acid hydrolases genetic control

Analysis of the genetic control of enzymes in animal cells has heen enhanced in recent years hy the availability of mutants in strains of inbred mice which exhibit altered enzyme phenotypes. Although many of these mutants are simple structural variants, several apparently involve more complex mechanisms of expression. Among these are two independent genetic factors which control phenotypic features of the acid hydrolase, jS-glucuronidase. 

Fig. 2. Simplified schema for the integration of acid hydrolase biosynthesis and ixissible sites of control Acid hydrolase biogenesis would be determined and controlled genetically via mRNA coding. Full biological expression requires ribosome-imlysome formation, membrane attachment ( stereoorientation) and formation of the enzyme-synthesizing unit...

A search for lysosomal hydrolases and related enzymes has been made in haemolysates from human and rabbit red cells. Apart from acid phosphatases, significant activities were found only for a-D-mannosidase, neutral o-D-glucosidase, and -D-2-acetamido-2-deoxyhexosidase. a-D-Mannosidase activity per cell in human red blood cells was 200-times lower than in white cells. The optimal pH was 5.5-6.0. Electrophoresis on cellulose acetate showed three bands. Haemolysates from four patients with mannosidosis were not deficient in a-D-mannosidase. Curves of pH activity and electrophoretic patterns were similar to those of controls. From its biochemical and genetic properties, it is concluded that red cell a-D-mannosidase differs from the lysosomal acid a-D-mannosidase. 

Compartmentalization of the genetic material (chromatin) into the eukaryotic nucleus is so widespread that its survival value cannot be doubted. As discussed in Chapter 13, such compartmentalization confers profound control capabilities on the cell while, in this instance, protecting the precious information contained in the DNA from gratuitous destruction by cytoplasmic hydrolases (Chapter 5). The chromatin of the nucleus is composed of deoxyribonucleic acid (DNA), histones... 

---