S. Vandijk et Dn. Ward, HETEROGENEITY IN PORCINE PITUITARY LUTEINIZING-HORMONE - AMINO-ACID AND CARBOHYDRATE ANALYSIS, Endocrinology, 130(4), 1992, pp. 1966-1974
Pituitary LH from porcine pituitary glands was purified by a buffered
ethanol extraction procedure, ion exchange on DEAE- and carboxymethyl-
cellulose, and molecular exclusion on Sephacryl S-200. Purity was asse
ssed by amino acid composition, N-terminal sequence, and polyacrylamid
e gel electrophoresis. Subunits were isolated by countercurrent distri
bution and reverse phase HPLC. Four major forms of the alpha-subunit w
ere detected: 1-96 (50%), 3-96 (23%), 4-96 (16%), and 7-96 (11%). [The
original sequence report described only the 7-96 form, but we have de
tected the other forms in our studies of porcine FSH and in this and o
ther species of LH.] Comparable N-terminal heterogeneity was not obser
ved for the beta-subunit. Additional heterogeneity was observed for bo
th subunits, atrributable to heterogeneity in the N-linked oligosaccha
ride moieties. The ioslated subunits were submitted to detailed compos
tional carbohydrate analysis, using pulsed amperometric detection of t
he HPLC-resolved sugar monomers after trifluoroacetic acid hydrolysis.
Sialic acid and sulfate esters were estimated on separate hydrolyzate
s. The compositional data suggest that the two alpha-subunit N-linked
moieties are hybrid complex biantennary structures with sulfated N-ace
tylgalactosamine (40-50%). Sixty to 70% of the alpha-subunit oligosacc
harides are fucosylated. The beta-subunit of porcine LH has a single g
lycosylation site, which contains a mixture of biantennary oligosaccha
ride chains (80-90%) ending in N-acetylgalactosamine, half of which ar
e sulfated. The balance (10-20%) are hybrid chains ending in sialylate
d galactose. The majority of the oligosaccharide on the beta-subunit i
s fucosylated.