Carbonic anhydrase (CA III) and myoglobin contents from isolated human muscle fibers were quantified using a sensitive time-resolved fluoroimmunoassay. Human psoas muscle specimens were freeze-dried, and single fibers were dissected out and classified into type I, IIA and IIB by myosin ATPase staining. Fiber typing was further confirmed by SDS-PAGE. CA III and myoglobin were found in all fiber types. Type I fibers contained higher concentrations of CA III and myoglobin than type IIA and IIB fibers. The relative concentrations of CA III in type IIA and IIB fibers were respectively 24% and 10% of that in type I fibers. The relative concentrations of myoglobin in type IIA and IIB fibers were 60% and 28% of that in type I fibers. Anti-CA III immunoblotting results from fiber-specific pooled samples agreed well with quantitative measurements. The results indicate that CA III is a more specific marker than myoglobin for type I fibers.

The lipoxygenase (LOX) in grass carp can catalyze the oxidation of polyunsaturated fatty acids even their esters, resulting in rancidity deterioration of grass carp and its products during the process and storage. Preliminary purification, quantitative determination and distribution of grass carp muscular LOX were investigated in the present study. LOX activity of the grass carp muscle was measured to be 35.17 KU/g and its molecular weight was 95.71 kDa identified by SDS-PAGE. Using previously reported extraction methods such as twice salting-out and once dialysis, the LOX protein content in the crude muscular LOX extraction is about 28%. When salted with graded saturation of ammonium sulfate, we found once salting-out was enough for LOX extraction and the effective percentage saturation of ammonium sulfate for LOX extraction was 40%. Under this condition, the LOX protein content in the crude muscular LOX extract was doubled. The LOX distribution in fish was gradually increased from skin and muscle, gill, viscera to blood, which indicates that it is very important to remove the viscera and bleed fish completely during fish product processing to decrease the risk of lipid oxidation caused by LOX.