To identify DNA markers associated
with performance, carcass, and meat production traits
including muscle postmortem cathepsin activity, several
porcine genes encoding for lysosomal proteinases
(cathepsin B, CTSB; cathepsin D, CTSD; cathepsin F,
CTSF; cathepsin H, CTSH; cathepsin L, CTSL; and
cathepsin Z, CTSZ) and for a cathepsin inhibitor (cystatin
B) were investigated. Single nucleotide polymorphisms
were identified in CTSD, CTSH, CTSL, and
CTSZ genes with a combination of in silico expressed
sequence tag database mining and single-strand conformation
polymorphism analysis. Sequencing and PCRRFLP
protocols were used to validate the identified
polymorphisms. Allele frequencies at these loci were
investigated in Italian Large White, Landrace, Duroc,
Piétrain, Belgian Landrace, Hampshire, and Meishan
breeds. Genotyping CTSD and CTSH markers made it
possible to genetically map these genes to SSC 2 and
7, respectively. Markers in CTSD, CTSH, CTSL, and
CTSZ genes, together with mutations we previously reported
in cystatin B, CTSB, and CTSF genes, were
genotyped in an Italian Large White sib-tested population
(272 or 482 animals). For these animals, meat
quality traits (cathepsin B activity, pH measured at 2 h
postmortem, pH measured at 24 h postmortem, glycogen,
lactate, and glycolytic potential of semimembranosus
muscle) and EBV for ADG, lean cuts (LC), backfat
thickness (BFT), ham weight (HW), and feed:gain ratio
(FGR) were determined. Analyzed markers did not
show any association with muscle cathepsin B activity.
Thus, it could be possible that different genes, other
than these investigated candidates, affect this trait,
which is correlated with the excessive softness defect
of dry-cured hams. The results of association analysis
confirmed the effects we already reported in another
study for CTSF on ADG (P = 0.008), LC (P = 0.001),
and BFT (P = 0.02). Moreover, CTSD was associated
with ADG, LC (P < 0.0001), BFT, HW, and FGR (P < 0.001); CTSH was associated with FGR (P = 0.026); and CTSZ was associated with ADG (P = 0.006), LC (P = 0.01), HW (P = 0.024), and FGR (P = 0.029). The biochemical and physiological functions of the lysosomal proteinases, together with the results obtained in our investigation, suggest that the cathepsin gene family might play important roles affecting economic traits in pigs.