The distribution and kinetic properties of guanylate cyclase in normal, denervated and dystrophic muscle from lower hind limb muscle of rat and mouse were studied. Approximately 75% of the enzyme activity was in a high speed supernatant fraction (100.000 x g) and 15 to 20% in a particulate fraction (1,000 x g pellet). The particulate guanylate cyclase was found highly enriched in sarcolemma, increasing over 100-fold in specific activity. Following denervation the sarcolemmal and supernatant enzymes increased concomitantly and were 2-fold higher by 10 days. The Vmax of sarcolemmal guanylate cyclase increased from 1600 to 2800 pmol.5 min-1.mg of protein-1 over this period. The S0.5 (0.13 mM), Hill coefficient (n= 1.7), Mn2+ dependency, inhibition by Ca2+, and degree of stimulation by Triton X-100 remained unchanged. Likewise, the Vmax of the 100,000 x g supernatant enzyme increased from 80 to 200 pmol.5 min-1. mg-1 with no change in the apparent Km (0.043 mM), Hill coefficient (n= 0.95), Mn2+ dependency, and degree of stimulation by Ca2+. The specific activity of particulate and supernatant enzymes was 2-fold higher in slow muscle (soleus) than in fast (extensor digitorum longus). Denervation increased the specific activity by approximately 2-fold in all cases. In mouse dystrophic muscle (129 ReJ dy/dy), the specific activity of the supernatant enzyme was 2.5-fold greater than that of control litter mates, while the particulate enzyme showed little change. Thus, the activities of particulate and soluble guanylate cyclase can change in a parallel fashion, as in denervation and in slow compared to fast muscle, and also can vary independently, as in dystrophic compared to normal muscle.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|State||Published - 1978|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology