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Calcium-activated neutral protease in the peripheral nerve, which requires microM order Ca2+, and its effect on the
Abstract:
There are two types of calcium-activated neutral protease (CANP), m-CANP and mu-CANP, following the nomenclature of Suzuki et al to show that each requires mM and microM Ca2+, respectively, for its activation. We found mu-CANP activity in a crude CANP fraction extracted from the peripheral nerve, which degraded the neurofilament (Nf) triplet (200 K, 160 K, 68 K), especially the 160 K component, at Ca2+ concentrations of 50 microM and 0.1 mM. The triplet was degraded in the order of the 160 K, 68 K, and 200 K components, respectively. In addition, the effects of partially purified mu-CANP of rabbit skeletal muscle, purified natural mu-CANP of bovine liver, derived mu-CANP prepared by autodigestion of chicken muscle m-CANP, m-CANP of chicken skeletal muscle, and cathepsin B of rat liver on the Nf were examined. Among the triplet components, the 160 K component was most rapidly degraded by all proteases so far tested. The difference in the effect of mu-CANP and m-CANP or cathepsin B on susceptibility of the 200 K component to degradation might be due to the difference of the relative amounts of enzymes to Nf.
Insights
Calcium-activated neutral proteases (CANP) like mu-CANP degrade neurofilaments (Nf), particularly the 160 K component. Different CANP types and concentrations affect Nf degradation rates.
Area of Science:
- Neuroscience
- Biochemistry
- Protease research
Background:
- Two types of calcium-activated neutral proteases (CANP) exist: m-CANP (mM Ca2+ activation) and mu-CANP (microM Ca2+ activation).
- Neurofilaments (Nf) are crucial structural components of neurons.
Purpose of the Study:
- To investigate the activity of mu-CANP on neurofilament degradation.
- To compare the degradation patterns of neurofilaments by different proteases.
Main Methods:
- Extraction and partial purification of mu-CANP from peripheral nerve.
- Incubation of neurofilament triplet proteins with various CANP types and cathepsin B.
- Analysis of neurofilament degradation patterns at different calcium concentrations.
Main Results:
- Mu-CANP activity was detected in peripheral nerve fractions, degrading the neurofilament triplet (200 K, 160 K, 68 K) at microM and mM Ca2+ levels.
- The 160 K neurofilament component was most rapidly degraded by all tested proteases, including mu-CANP, m-CANP, and cathepsin B.
- Degradation order for the neurofilament triplet by mu-CANP was 160 K, 68 K, and 200 K.
Conclusions:
- Mu-CANP plays a significant role in neurofilament degradation.
- The 160 K neurofilament subunit is particularly susceptible to proteolysis by various proteases.
- Differences in enzyme-to-substrate ratios may influence the degradation susceptibility of the 200 K neurofilament component.