  We present a study of the bulge-to-total ratio (B/T) of a Ks-band-selected
sample of 88 close major-merger pairs of galaxies (H-KPAIR) based on 2-D
decomposition of SDSS r-band images with \textsc{galfit}. We investigate the
dependence of the interaction-induced specific star formation rate enhancement
($\rm sSFR_{enh}$) on the B/T ratio, and the effects of this dependence on the
differences between star-forming galaxies (SFGs) in spiral+spiral (S+S) and
spiral+elliptical (S+E) pairs. Of all 132 spiral galaxies in H-KPAIR, the 44 in
S+E pairs show higher B/T than those in the 44 S+S pairs, with means of $\rm
B/T = 0.35 \pm 0.05$ and $\rm B/T = 0.26 \pm 0.03$, respectively. There is a
strong negative dependence of $\rm sSFR_{enh}$ on the B/T ratio and only paired
SFGs with $\rm B/T<0.3$ show significant ($>5\sigma$) enhancement. Paired SFGs
in S+S pairs show a similar trend, and many disky SFGs ($\rm B/T<0.1$) in S+S
have strong sSFR enhancements ($\rm sSFR_{enh} > 0.7$~dex). For SFGs in S+E,
the sSFR has no clear B/T dependence, nor any significant enhancement in any
B/T bin. Disky SFGs in S+S show significant ($>4\sigma$) enhancement in the
molecular gas content ($\rm M_{H_2}/M_{star}$), while SFGs in S+E have no such
enhancement in any B/T bin. No significant enhancement on total gas content
($\rm M_{gas}/M_{star}$) is found in any B/T bin for paired galaxies. The star
formation efficiency of either the total gas ($\rm SFE_{gas} = SFR/M_{gas}$) or
the molecular gas ($\rm SFE_{H_2} = SFR/M_{H_2}$) does not depend on the B/T
ratio. The only significant ($>4\sigma$) SFE enhancement found for paired SFGs
is the $\rm SFE_{gas}$ for disky SFGs in S+S pairs.
