enzymes that catalyze the reversible aldol cleavage of fructose 1,6-bisphosphate
to dihydroxyacetone phosphate
and either glyceraldehyde 3-phosphate
, respectively. Three aldolase isozymes are found in mammals, specifically aldolases A, B, and C, each of which is encoded by a separate gene.
Aldolase A is generally considered to be a muscle enzyme. Northern analysis of cultured cells suggests that it is present in both neurons and glia (1). Aldolase B is considered to be a liver-specific enzyme and it is transcriptionally activated by signals from hormones and dietary factors (2). In the adult, aldolase C is the brain-specific isozyme, with low but detectable activity in fetal tissues (1, 3-6). Aldolase C shares 81% amino acid identity with aldolase A and 70% identity with aldolase B.
Earlier studies using isozyme-specific antibodies report its location in gray matter astrocytes and cells of the pia mater (5, 8). In situ hybridization of mouse central nervous system using isozyme-specific probes revealed that aldolase A and C are expressed in complementary cell types: aldolase A mRNA is found in neurons; aldolase C message is detected in astrocytes, some cells of the pia mater, and Purkinje cells (9). Aldolase C can in some situations be used as an astrocyte marker. However Purkinje cells of the cerebellum contain high levels of the enzyme, so the enzyme is not totally astrocyte specific.
MCA-1A1 was raised against C-terminal 23 amino acids of aldolase C protein, the sequence is KYEGSGEDGGAAAQSLYIANHAY. The HGNC name for this protein is ALDOC.
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3. Mukai T, Yatsuki H, Masuko S, Arai Y, Joh K & Hori K. The structure of the brain-specific rat aldolase C gene and its regional expression. Biochem. Biophys. Res. Commun. 174, 1035-1042 (1991).
4. Royds J, Ironside J, Warnaar S, Taylor C & Timperle W. Monoclonal antibody to aldolase C: a selective marker for Purkinje cells in the human cerebellum. Neuropathol. Appl. Neurobiol. 13, 11-21(1987).
5. Thompson R., Kynoch P. Willson V. Cellular localization of aldolase C subunits in human brain. Brain Res. 232, 489-493 (1982).
6. Schapira F, Reuber M, Hatzfeld A. Resurgence of two fetal-type of aldolases (A and C) in some fast-growing hepatomas. Biochem. Biophys. Res. Commun. 40, 321-327(1970).
7. Arai Y, Kajihara S, Masuda J, Ohishi S, Zen K, Ogata J. Mukai T. Position-independent, high-level, and correct regional expression of the rat aldolase C gene in the central nervous system of transgenic mice. Eur. J. Biochem. 221, 253-260 (1994).
8. Wachsmuth E, Thorner M. & Pfleiderer G. The cellular distribution of aldolase isozymes in rat kidney and brain determined in tissue sections by the immuno-histochemical method. Histochemistry, 45, 143-161 (1975).
9. Walther EU, Dichgans M, Maricich SM, Romito RR, Yang F, Dziennis S, Zackson S, Hawkes R, Herrup K. Genomic sequences of aldolase C (Zebrin II) direct lacZ expression exclusively in non-neuronal cells of transgenic mice. Proc Natl Acad Sci U S A. Mar 3;95(5):2615-20(1998).