Imaging agents that can bind to ghrelin O-acyltransferase (GOAT) without binding to the ghrelin receptor (GHS-R1a). The imaging agents comprise a base structure for selective binding to GOAT that is coupled via an amino acid linker to a chemical group to enable imaging such as a fluorescent label, radioactive tracer, or metal chelator. For example, the imaging agent may comprise a ghrelin substrate mimetic inhibitor incorporating an unmodified 2,3-diaminopropanoic acid (Dap) group at the site analogous to serine 3. These agents enable specific detection and imaging of GOAT versus the GHS-R1a receptor in a variety of biological contexts.

Imaging agents that can bind to ghrelin O-acyltransferase (GOAT) without binding to the ghrelin receptor (GHS-R1a). The imaging agents comprise a base structure for selective binding to GOAT that is coupled via an amino acid linker to a chemical group to enable imaging such as a fluorescent label, radioactive tracer, or metal chelator. For example, the imaging agent may comprise a ghrelin substrate mimetic inhibitor incorporating an unmodified 2,3-diaminopropanoic acid (Dap) group at the site analogous to serine 3. These agents enable specific detection and imaging of GOAT versus the GHS-R1a receptor in a variety of biological contexts.

Imaging agents that can bind to ghrelin O-acyltransferase (GOAT) without binding to the ghrelin receptor (GHS-R1a). The imaging agents comprise a base structure for selective binding to GOAT that is coupled via an amino acid linker to a chemical group to enable imaging such as a fluorescent label, radioactive tracer, or metal chelator. For example, the imaging agent may comprise a ghrelin substrate mimetic inhibitor incorporating an unmodified 2,3-diaminopropanoic acid (Dap) group at the site analogous to serine 3. These agents enable specific detection and imaging of GOAT versus the GHS-R1a receptor in a variety of biological contexts.

Imaging agents that can bind to ghrelin O-acyltransferase (GOAT) without binding to the ghrelin receptor (GHS-R1a). The imaging agents comprise a base structure for selective binding to GOAT that is coupled via an amino acid linker to a chemical group to enable imaging such as a fluorescent label, radioactive tracer, or metal chelator. For example, the imaging agent may comprise a ghrelin substrate mimetic inhibitor incorporating an unmodified 2,3-diaminopropanoic acid (Dap) group at the site analogous to serine 3. These agents enable specific detection and imaging of GOAT versus the GHS-R1a receptor in a variety of biological contexts.

An intracellular selection system allows screening for peptide bioactivity and stability. Randomized recombinant peptides are screened for bioactivity in a tightly regulated expression system, preferably derived from the wild-type lac operon. Bioactive peptides thus identified are inherently protease- and peptidase-resistant. Also provided are bioactive peptides stabilized by a stabilizing group at the N-terminus, the C-terminus, or both. The stabilizing group can be a small stable protein, such as the Rop protein, glutathione sulfotransferase, thioredoxin, maltose binding protein, or glutathione reductase, an -helical moiety, or one or more proline residues.

An intracellular selection system allows screening for peptide bioactivity and stability. Randomized recombinant peptides are screened for bioactivity in a tightly regulated expression system, preferably derived from the wild-type lac operon. Bioactive peptides thus identified are inherently protease- and peptidase-resistant. Also provided are bioactive peptides stabilized by a stabilizing group at the N-terminus, the C-terminus, or both. The stabilizing group can be a small stable protein, such as the Rop protein, glutathione sulfotransferase, thioredoxin, maltose binding protein, or glutathione reductase, an -helical moiety, or one or more proline residues.

Ghrelin signal peptide fragment assays and kits useful in the diagnosis, prognosis, risk stratification, assessing, staging, monitoring, categorizing and determination of further diagnoses and treatment regimens in subjects with various disorders, diseases and conditions including, pneumonia, heart failure, or pneumonia and heart failure or suspected pneumonia, heart failure, or pneumonia and heart failure, and methods for monitoring treatment.

Ghrelin signal peptide fragment assays and kits useful in the diagnosis, prognosis, risk stratification, assessing, staging, monitoring, categorizing and determination of further diagnoses and treatment regimens in subjects with various disorders, diseases and conditions including, pneumonia, heart failure, or pneumonia and heart failure or suspected pneumonia, heart failure, or pneumonia and heart failure, and methods for monitoring treatment.

A polypeptide cleavage method characterized in that arginine or lysine is at the P1 position of a desired cleavage site in a polypeptide, an amino acid other than aspartic acid, glutamic acid or proline is at the P1 position, a single basic amino acid or two or three consecutive basic amino acids are situated at any site in the amino acid sequence from the P10 position to the P3 position or from the P3 position to the P5 position (with the proviso that a single basic amino acid is not situated at the P6 or P4 position), and OmpT protease or its variant enzyme having a substitution at the 97th amino acid from the N-terminus is used to cleave the desired cleavage site in the polypeptide.

A polypeptide cleavage method characterized in that arginine or lysine is at the P1 position of a desired cleavage site in a polypeptide, an amino acid other than aspartic acid, glutamic acid or proline is at the P1 position, a single basic amino acid or two or three consecutive basic amino acids are situated at any site in the amino acid sequence from the P10 position to the P3 position or from the P3 position to the P5 position (with the proviso that a single basic amino acid is not situated at the P6 or P4 position), and OmpT protease or its variant enzyme having a substitution at the 97th amino acid from the N-terminus is used to cleave the desired cleavage site in the polypeptide.