1. Collagenolytic enzyme activity in human ovary: an ovulatory enzyme system
M Fukumoto, Y Yajima, H Okamura, O Midorikawa Fertil Steril. 1981 Dec;36(6):746-50. doi: 10.1016/s0015-0282(16)45920-0.
Collagenolytic enzyme activities presumed to play an important role in ovulation were investigated in the human follicular apex, base, and granulosa cell layer throughout the ovarian cycle. Those analyzed were human ovarian collagenase, 2,4-dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg-OH peptidase, N-carbobenzoxy-Gly-Pro-Gly-Gly-Pro-Ala peptidase, and alpha-N-benzoyl-DL-arginine beta-naphthylamide hydrolase. Collagenase activity was also measured in human granulosa cell cultures. The activities of all four enzymes showed a marked preovulatory decrease in the apex. The activities in the apex were slightly higher than those in the base throughout the ovarian cycle. However, the activities in the granulosa cell layer and collagenase activity in the granulosa cell cultures increased toward preovulation and decreased after ovulation. These findings suggest that collagenase is synthesized in the granulosa cells maximally at preovulation and is consumed in the follicular apex at the same time, resulting in collagen degradation and disruption of the follicular wall in collaboration with other collagenolytic enzymes investigated here.
2. Fragmentation reactions of protonated peptides containing glutamine or glutamic acid
Alex G Harrison J Mass Spectrom. 2003 Feb;38(2):174-87. doi: 10.1002/jms.427.
A variety of protonated dipeptides and tripeptides containing glutamic acid or glutamine were prepared by electrospray ionization or by fast atom bombardment ionization and their fragmentation pathways elucidated using metastable ion studies, energy-resolved mass spectrometry and triple-stage mass spectrometry (MS(3)) experiments. Additional mechanistic information was obtained by exchanging the labile hydrogens for deuterium. Protonated H-Gln-Gly-OH fragments by loss of NH(3) and loss of H(2)O in metastable ion fragmentation; under collision-induced dissociation (CID) conditions loss of H-Gly-OH + CO from the [MH - NH(3)](+) ion forms the base peak C(4)H(6)NO(+) (m/z 84). Protonated dipeptides with an alpha-linkage, H-Glu-Xxx-OH, are characterized by elimination of H(2)O and by elimination of H-Xxx-OH plus CO to form the glutamic acid immonium ion of m/z 102. By contrast, protonated dipeptides with a gamma-linkage, H-Glu(Xxx-OH)-OH, do not show elimination of H(2)O or formation of m/z 102 but rather show elimination of NH(3), particularly in metastable ion fragmentation, and elimination of H-Xxx-OH to form m/z 130. Both the alpha- and gamma-dipeptides show formation of [H-Xxx-OH]H(+), with this reaction channel increasing in importance as the proton affinity (PA) of H-Xxx-OH increases. The characteristic loss of H(2)O and formation of m/z 102 are observed for the protonated alpha-tripeptide H-Glu-Gly-Phe-OH whereas the protonated gamma-tripeptide H-Glu(Gly-Gly-OH)-OH shows loss of NH(3) and formation of m/z 130 as observed for dipeptides with the gamma-linkage. Both tripeptides show abundant formation of the y(2)'' ion under CID conditions, presumably because a stable anhydride neutral structure can be formed. Under metastable ion conditions protonated dipeptides of structure H-Xxx-Glu-OH show abundant elimination of H(2)O whereas those of structure H-Xxx-Gln-OH show abundant elimination of NH(3). The importance of these reaction channels is much reduced under CID conditions, the major fragmentation mode being cleavage of the amide bond to form either the a(1) ion or the y(1)'' ion. Particularly when Xxx = Gly, under CID conditions the initial loss of NH(3) from the glutamine containing dipeptide is followed by elimination of a second NH(3) while the initial loss of H(2)O from the glutamic acid dipeptide is followed by elimination of NH(3). Isotopic labelling shows that predominantly labile hydrogens are lost in both steps. Although both [H-Gly-Glu-Gly-OH]H(+) and [H-Gly-Gln-Gly-OH]H(+) fragment mainly to form b(2) and a(2) ions, the latter also shows elimination of NH(3) plus a glycine residue and formation of protonated glycinamide. Isotopic labelling shows extensive mixing of labile and carbon-bonded hydrogens in the formation of protonated glycinamide.
3. Isolation and amino acid sequence of gamma-lipotropin from human pituitary glands
C H Li, D Chung, D Yamashiro Proc Natl Acad Sci U S A. 1980 Dec;77(12):7214-7. doi: 10.1073/pnas.77.12.7214.
gamma-Lipotropin has been purified to homogeneity from human pituitary glands. It consists of 56 amino acids with one residue each of Trp, Thr, Val, Tyr, and Phe. The amino acid sequence has been determined as follows: H-Glu-Leu-Thr-Gly-Gln-Arg-Leu-Arg-Gln-Gly-Asp-Gly-Pro-Asn-Ala-Gly-Ala-Asp-Asp-G ly-Pro-Gly-Ala-Gln-Ala-Asp-Leu-Glu-His-Ser-Leu-Leu-Val-Ala-Ala-Glu-Lys-Lys-Asp- Glu-Gly-Pro-Tyr-Arg-Met-Glu-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-Lys-Asp-OH. Comparison with the structure of the ovine and porcine hormones reveals that the 23-amino-acid sequence at the COOH terminus is highly conserved in evolution.
