The subcellular distribution of carnosine, carnosine synthetase, and carnosinase in mouse olfactory tissues

The dipeptide, carnosine, its synthetic enzyme, carnosine synthetase, and its degradative enzyme, carnosinase, appear to be localized in the cytosol of mouse olfactory bulb and epithelium. Mouse olfactory bulbs and epithelium were prelabeled in vivo with [ 3H]carnosine following intranasal irrigation with [ 3H]β-alanine. [ 3H]-carnosine co-distributed in olfactory bulb with lactate dehydrogenase with only 10% in the crude mitochondrial fraction. Similar results were also seen with endogenous carnosine distribution. Over 70% of the carnosine present in the crude mitochondrial fraction was localized in synaptosomes following sucrose gradient centrifugation. However, further fractionation of vesicle containing fractions from osmotically lysed crude mitochondrial fractions indicated that [ 3H]carnosine was not associated with vesicles. Nearly 70% of all the [ 3H]carnosine present in olfactory epithelium was soluble with most of the remainder in the crude nuclear fraction. The enzymes carnosine synthetase and carnosinase were clearly soluble in olfactory epithelium with 98% and 85% of the activity in the cytosol. Less than 2% was found in the crude mitochondrial fraction. In olfactory bulb both enzymes also appeared soluble.