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prostatic acid phosphatase (PAP) 597 proteasome
OH
OH OH
Prostaglandin F 2 α
O
OH
COOH
OH
Prostaglandin E 2
OH
Prostaglandin D 2
COOH
nonsuspicious digital rectal examinations are generally not
biopsied for prostate cancer. Men with PSA levels of 10.0
ng/mL and above typically undergo prostate biopsies. About
one half of these men will have prostate cancer. Certain
types (bound PSAs) link themselves to other proteins in the
blood. Other kinds (free PSAs) float alone. Prostate cancer
is more likely to be present in men who have low percentages
of free PSA relative to the total amount. This finding is
especially valuable in helping differentiate cancer and other
benign conditions, thus eliminating unnecessary biopsies
among men in the diagnostic gray zone (total PSA levels
from 4.0 to 10.0 ng/mL). The PSA molecule is smaller than
prostatic acid phosphatase (PAP). In patients with prostate
cancer, preoperative PSA serum levels are positively
correlated with the disease. PSA is increased in 95% of
new cases of prostatic carcinoma, and in 97% of recurrent
cases. It is inappropriate to use PSA levels alone to screen
asymptomatic males. TUR, urethral instrumentation, prostatic
needle biopsy, prostatic infarct, or urinary retention
may also result in increased PSA values. PSA is critical
for the prediction of recurrent adenocarcinoma in postsurgical
patients. In a minority of cases of prostate cancer,
especially those confined to the prostate, serum PSA is not
elevated. Refinements in PSA testing values increased its
diagnostic significance. This includes rate of change of PSA
values with time, i.e., PSA velocity, determination of the
ratio of serum PSA value and volume of the prostate gland,
i.e., PSA density, and the measurement of free versus bound
forms of circulating PSA. Free PSA levels >25% suggest
a lower risk for cancer; levels below 10% are bothersome.
O
COOH
OH
Prostaglandins, which are released and facilitate mediation of type I hypersensitivity
reactions.
Prostate-specific antigen (PSA)⎯prostate.
These parameters may be most useful when PSA levels
range between 4.0 and 10.0 ng/ml, the so-called gray zone.
PSA is also a useful immunocytochemical marker for primary
and metastatic adenocarcinoma of the prostate.
prostatic acid phosphatase (PAP)/prostatic epithelial antigen
Prostate antigens, identifiable by immunoperoxidase staining.
They are prostate-specific and -sensitive. Used together, they
detect approximately 99% of prostatic adenocarcinomas.
pro-T cell
The earliest identifiable thymocyte recognized by expression
of cell surface antigens such as CD2 and CD7 and
by CD3 ε protein in the cytoplasm, but absent from cell
surfaces. Rearrangement of δ, γ, and β TCR genes accompanies
differentiation of pro-T cells into pre-T cells.
protease (HIV)
One of the HIV viral enzymes that splits polyprotein precursors
to yield mature viral constituents.
148Å
113Å
13Å
27Å
Catalytic
sites
Longitudinal and transverse section through the 20S proteasome composed
of two outer and two inner rings. The two outer rings each comprise seven
copies of the 25.9-kDa α subunit.
proteasome
A large (650-kDa) organelle in the cytoplasm termed the low
molecular mass polypeptide complex. The proteasome is
believed to generate peptides by degradation of proteins in the
cytosol. It is a cylindrical structure composed of as many as
24 protein subunits that participates in degradation of proteins
in the cytosol that are covalently linked to ubiquitin. It is
necessary for some protein antigens to be ubiquinated prior to
presentation to major histocompatibility complex (MHC) class
I-restricted T lymphocytes. Proteasomes that include MHC
gene-encoded subunits are especially adept at forming peptides
that bind MHC class I molecules. A strategic part of the
endogenous antigen processing and presentation pathway. In
resting cells, the standard proteasome digests mostly undesired
self proteins. In dendritic cells and other cells accompanying
inflammation, the immunoproteasome functions to digest
foreign proteins.
α
β
β
α
P